To answer the original question: Is a 92FS really any less safe than a Glock when carried this way?
Yes.
As others have posted, the Glock is only partially cocked when it is carried, and has safeties that require that the trigger being squarely and fully depressed. Dave T's post sums it up well.
Most defensive instructors and schools advocate a trigger pull of 4-5 pounds as a minimum. and I haven't seen any that recommend the Glock 3.5lb connector for carry use, much less tout it as the ideal carry setup.
Carrying a 92FS condition zero is less safe. The hammer is fully cocked, and there is nothing to prevent discharge from an errant side loading from holster body, retention strap, etc.
How many stories of accidental discharges have you hear about with Glocks? How many have you heard about with the M9 or LE Beretta's or SIG's or HK's?
Accidental discharges happen in all these weapons, and are caused by defective operation of the cop's fingers, not any safety mechanism or lack thereof. Glocks seem to have more discharges due to officers failing to clear their weapon properly before attempting to strip/function check it. This is a training issue more than a design issue. Most LE are not shooting enthusiasts, and know only what training has covered. Glocks are the most commonly issued firearms in US LE service, so the fact that they have more "stories" about NDs would not be that shocking.
Could a 92, with the proper training and leather, be carried safely this way? Sure. So could a condition zero Sig, Browning, HK, or 1911. Even in the (extremely rare) instance of a outright sear breakage, firing pin blocks or half cock notches or a combination of the two would most likely prevent a discharge. That doesn't make it a good idea. Reholstering quickly would be very touchy, or slower than the conventional methods.
If you have trouble with managing the trigger in an SA/DA pistol, rather than carrying the weapon in a manner which is inherently less safe than the than TDA or C&L, either practice it until it is no longer an issue, or choose a different weapon that can use a consistent pull for every shot. Whether that is a CZ/BHP/HKUSP/1911 carried C&L, a "safe action" type such as the Glock, XD or (shudder) a DAO, such as Beretta 92G, H&K V5, P2000, is up to you.