wrote:

I still don't get it.

What does descending to 250 ft vs 200 ft on an approach have to do
with wingtip spacing or back-taxi operations?


I believe wingtip spacing has to do with the lowest visibility that can be
authorized. One location I am familiar with is KCRQ where the ILS vis was increased
from 2400 to 4000 because the taxiway was too close for Dash 8 aircraft to use at RVR
2400.

I do not have experience with how the airport design folks think. If you want to
know more, I recommend you look at the airport ACs.

As to back-taxi, I guess it becomes an issue of having sufficient visibility to see
and avoid the aircraft on the runway coming at you.