Not really, at least not in the way I think you mean it. What has been determined is that it affects some people far less than others ... the kind usually chosen to be astronauts, fighter pilots, etc.
Again ... not really. Some manufacturers are quite clear that the slide stop is not a slide release. All this really means is that people should stop preaching one method or the other as if it is some universal holy writ.
The reasoning behind using the slide release is sound, if you have a gun designed to work that way and your goal is shaving 10ths of seconds off of a reload. There are observable issues with this method, if your concern is more tilted towards robust reliability under genuine fear-for-your-life levels of stress.
The reasoning behind racking the slide is sound, if your goal is achieving a consistent, reliable technique with the fewest number of technical issues over a wide range of firearm designs. That's probably why so many defensive instructors teach it ... teaching one thing which works almost perfectly for almost everyone is a better use of training time, than getting into every little individual special-snowflake combination of gear and personal preferences. I can't see how it can ever be faster, but perhaps it gains something in reliability under real stress.
You got any citations or proof of that, or are you talking out of your ass? Name some names. Which manufacturers?
Midvalley is right. JMB designed it to be used that way, and everyone since has copied his design.
Some more interesting tidbits about what the 1911's various parts "were designed for"
Patent US708794 - AUTOMATIC FIREARM - Google Patents
The breech remainingthus wide open serves as an unmistakable
indication that the magazine is empty and for
continued firing must be replaced by a loaded 125
one. This is now readily and safely accomplished
by withdrawing the empty magazine
from the grip and introducing a loaded one
while the breech remains open. · Then releasing
the breech-slide by pressing upon the 130
thumb-piece p' of the latch-slide the breech
will be automatically closed by the reactionspring
e, and the pistol will be ready again
Then, his later Patent 984519 on the 1911
Patent US984519 - MREARM - Google Patents
In order to adapt the handle to be readily moved upward and downward by the thumb of the hand grasping-the grip,the rear end of the handle j carries a projecting thumb piece j1
The inner lug j1 doe not interfer with the passage of the cartridges from the magazine to the chamber in the barrel,
‘ but when the last cartridge has been fed
from the magazine, the lug j2 stands in ‘the
path of the spring-follower of the magazine,
‘and when the breech-slide is moved to the
rear above the empty magazine, the follower"
' v will raise the ln j2 and the handle 2 and
.' cause the projection Z to enter the recess m
the breech-slide, thereby locking the‘ same
- in the open rear position. and serving as an‘
indicator to show that the empty magazine
must be replaced by a charged one before the
?ring can be continued. After placing the
magazine in the grip. the breech-slide is re
leased by depressing the handle j.