which other generally acknowledged DAO pistol does not have a 2nd strike capability?
S&W metal-framed DAO models.
Couldn't resist.
You're right in that everything else is silly to argue about, though.
One thought I'd like to express is an opinion that shooting to trigger reset in SA mode can be a potentially dangerous thing to do, depending on the circumstances.
Shooting to SA trigger reset in a dedicated safe target/bulls eye shooting situation is one thing, but trying to keep a finger on the trigger and only allow SA trigger recovery to the 'reset' point in any other conditions, especially those involving a perception of heightened risk and an unlawful threat of serious bodily injury or death, can arguably significantly elevate the potential risk of a ND.
I've seen any number of folks unintentionally 'double' when qualifying on a course of fire when they kept their fingers on the trigger after the intentional first shot. Some really surprised faces. In most cases it seemed to be caused by 'rocking under recoil' with a finger on the trigger, although I can think of some where the shooter seemingly just lost focus of what they were doing with their trigger finger, which was still on the trigger in SA mode, and they twitched or tightened their finger without realizing it. Not good when bullets fly unintentionally.
Now, S&W traditional double action pistols have always enjoyed the reputation of having the shortest and 'fastest' SA trigger reset among TDA semiauto pistols. (Although, the Walther AS model's single action sear function is pretty short in the 99 series, too.) When I attended a Sig armorer class I was told that the Short Reset Trigger option (a different sear and sear spring) had originally been designed to compete against S&W in a large LE contract bid, and that the new design was actually mechanically shorter in operation than the S&W design. If I remember right, someone from Sig at that class said the difference was something along the order of the Sig design having approx a 20 thousandths of an inch shorter SA reset. Maybe so. I couldn't tell the difference by finger, that's for sure.
Considering all the different handguns I shoot (revolver & pistol), I've long since reverted to having my trigger finger allow complete trigger recovery when shooting, even when shooting intentionally fast shot strings. It only took a few instances of short-stroking a trigger when using a different gun - (switching between different designs of semiauto pistols as well as between pistols & revolvers) - to convince me that full trigger recovery was a good thing in stressful situations.
If I'm working on a specific trigger press skill on a target/bulls eye range, that's one thing. If I'm working to complete a course of fire including multiple targets, movement across uneven ground, in variable/low light, as well as having to identify threat/non-threat situations, I let my trigger and finger fully recover and keep my finger away from the trigger between intentional shots.
Personally, I'd not like to try and explain to a jury how allowing a trigger to only recover to the 'reset point', and keeping my finger on it to keep it from moving farther forward in case I may decide to fire again ... and then having the gun unintentionally fire because of an interlimb interaction (also called sympathetic squeeze), which is the involuntary contraction of an individual’s hand and finger muscles ... is somehow different than just having a finger on the trigger and triggering a ND.
The fine distinction in intention might be lost on the jury.
There have been some excellently skilled 'trigger slappers' who showed that it was possible to shoot both fast and accurately when allowing full trigger recovery between each shot, too.
I cringe whenever I hear another instructor teaching someone to 'just let your trigger finger go forward until the trigger resets'. What are the circumstances being considered and addressed at the moment? Is it for shooting a timed bulls eye course of fire, where a fine SA trigger stroke using a competition trigger may mean the points for winning? Or, for if the shooter ever finds him/herself in a chaotic, rapidly changing, physically tumultuous life threatening situation when their fine motor skills may be in short supply and their attention and focus may be distracted from realizing a fraction of an inch of movement of their finger has occurred against a trigger face ... until it's too late?
As far as the original question?
Probably because different traditional double action (DA/SA) semiauto pistol designs have to accomplish both mechanical actions (DA & SA modes) taking into consideration the inherent limitations of combining both operations in their various designs. Some seem to have achieved it better than others.
Even the various DA/DAO trigger operations can have some variance in both trigger movement and trigger pull weight, though.
Then, there's the growing number of diverse designs which don't easily allow for them to be exactly pigeon-holed into the simple designations we've commonly accepted over the years.
Hey, just my thoughts. I'm certainly nobody's 'expert' anything at this stuff.
There are some serious potential issues to consider when discussing 'shooting to trigger reset', and discussing it in person with a trainer might offer some helpful insight into the subject.
