Technical difficulty is a static measure that isn't influenced by other variables unless those other variables actually change the dynamic of the route, like rain or ice.
You make some excellent points above.
Anyway, there are many added factors (such as exposure) too that add to a route even if technical difficulty stays the same.
One besides exposure is "rock quality." Last November, my borther, cousin, a friend, and myself went to climbWindow Blind Peak, a beautiful peak rising a few thousand feet above the desert in the San Rafael Swell in Utah. My cousin and his partner lead 5.12 trad, so I (and the others) thought the summit was in the bag. Though the easiest route up the peak is "only" 5.7 (though highly exposed), we didn't pull the summit block.
When I invited them, I failed to recognise that although they could lead 5.12, almost all their experience was on hard granite. The soft sandstone was something they were not used to and it was intimidating for them. I was used to soft rock, but am not very skilled in leading multi-pitch trad. Therefore, we failed to reach the summit.
There are many factors that play into a climb other than just technical difficulty. Exposure, rock quality, avy danger, etc. all play a part in how intimidating a route is.