The UV filters (and other "UVC" filters) are always on the outer surface of the objectives.
Right, throughout would be too much. But also, why allow a frequency with much higher
scattering on dust bits and walls to enter in the first place?
It's simply layers designed to reject violet a little and UV a lot, like the response of any
band-pass filter. Interference in coatings is always bandpass filtering. In the original single-layers,
violet and UV are rejected far more than the red end, because the violet end is extremely
prominent in haze over hundred yards.
If you lose a little blue, a bit more violet, and lots of UV, things far away don't actually look yellow,
because in fact your distant image is already 'violet-shifted' to start with. Your eyes also
automatically adjust color sensation, as they must to cover morning and dusk lighting.
People using 4mm and up for exit pupils should beware of bright backgrounds with
super-transmission lenses. Your eyes are being aged quickly, just like looking at
bright things without the lenses. You don't realize it as much because your AFOV is
not the same as the unaided eye. Also, blue and violet diminish your light sensitivity
more.