No need. There's nothing wrong with my handguns. You have described it right. At least the first part. On a Glock, the difference seems to be the barrel drops a lot more by the movement of the slide (moreso than gravity, I think), after unlocking. Of course this doesn't happen if you are pressing on the front of the barrel, like what would happen in a drop fire.
So after the initial 0.012-.015" of barrel drop in your 1911 (similar on a Glock), the firing pin will still be over a small or large pistol primer. That's as far as the barrel would drop. And the breech will not have separated away from the barrel, significantly, since there's nothing pushing the slide back. Hence it seems like it would still drop fire, even if the frame had moved that far down to completely unlock the action.
The disconnector should have tripped by now, but in a drop fire the disconnector doesn't matter. The firing pin is moving by inertia and bypassing the trigger/sear/hammer, altogether.
When the barrel hits the vertical impact surface
In a drop fire, this is the endpoint. When the barrel hits the vertical impact surface, it's done. And the slide is done. The frame/slide doesn't move in relation to each other past this point beyond what is due to the relatively trivial amount of momentum the slide receives when the barrel/slide bounce off the ground. Is this enough to separate the breech from the barrel far enough to get the firing pin out of range, and does this occur in time? This is the part I don't have a sure answer for, in practice, with a 1911, specifically. I don't think the firing pin generally has to move very far, so I suspect the majority of guns would still drop fire.