I only really button up when I see tracer come towards me, like machinegun fire for example, especially in the Tiger its quite rare to be killed by secondary fragmentation from bouncing shells, the Panther for example has that issue, when a shot bounces off your frontal plate you can run the danger of getting hit. Also another reason why I rarely button up is the visibility, in IL-2 99% of tank crew servers are exclusively First Person only, and with the "Mail slot" style vision Slits of the H1 the visibility is rather lackluster when buttoned up.

Its YT auto Detect, i sadly cant change it. This False Catigorization actually happens quite a lot with IL-2 Great Battles Tank Crew Content.