The large screw that blocks the trigger screw from being backed out holds the trigger assembly to the action. You remove it to swap out the spring inside. I can remove the screw and spring on mine and it will pass a bump test without dropping the firing pin. Anything can be adjusted out of limits to be unsafe, think Remington X mark triggers.I definitely will. Keep in mind I was told 10-12 weeks after shipped.
I will add something else. I pulled the other T3 out of the safe last night and there is a HUGE difference in the feel, stability and movement of the safety from one to the other.
Also let me be clear about the trigger pull. I have had the weapon for about 12 years and I can honestly say that I cannot remember ever adjusting the trigger--and I'm fairly certain I would remember doing that. I also looked very, very close at the screws that allow you to remove the action from the stock and I do not see any evidence they have had a tool in them. But from what I understand watching videos that allen screw cannot be backed out to the point where the rifle becomes unsafe. The photos I believe you posted above show a larger screw that is supposed to prevent that by stopping the screw from being backed out too far (unsafe).
Again, I love Tikka rifles--have 3 of them. But if they allow the end user to adjust the weapon's pull to the point it fires unintentionally that seems to me like a design flaw. Maybe thats just me.