One thing I'd definitely check is whether you can still manage to cock the hammer on the GP100. If the hammer was bobbed, the SA sear should have been eliminated, rendering the gun Double Action-Only; otherwise, one could cock the hammer and have no safe way (other than firing the gun) of de-cocking.
As mentioned, hammers are often bobbed to prevent snagging on clothing. Also, for a defense-only revolver, the gun is often rendered DAO for safety/liability reasons: the SA actions on DA revolvers are often quite light and crisp, so without a safety, it's a very bad idea to cock the hammer on a DA revolver when in defense mode, and with the hammer present, many shooters can get in the habit of cocking the hammer. What's odd is that a 4" GP100 isn't all that concealable, and if it were mine, I wouldn't limit it to defense-only.
How's the DA trigger? It's also possible someone had a good action job done on it - by eliminating the SA sear, the DA trigger can be tuned more radically, and with a light DA trigger pull that would otherwise result in a SA trigger pull that was far too light.