My 1970 39 Twin has always been in the family and it has always had the flush door flap with the turn tab to open with fuel cap underneath (thermos or now screw type) for mains and aux tanks. Tip tanks are the same except curved to follow tank profile. Webco nacelle tanks use flush door with screwdriver access and fuel cap underneath. Miller STC'd wet wing use an integrated handle that pops up, then twists and finally pulls out.

Can't speak for all Comanches, have flown other PA30s with the same set up. During very high prices, perhaps someone wnet to screwdriver approach to slow potential fuel theft.