BacK off week:recovery week?

week 1 5x5
week 2 5,4,3,2,1
week 3 10, 8, 6
week 4 3x3 (would this be a backoff week)

is the reduction in volume, with the intensity still high an appropriate backoff week?

thank you

(Quick, pioneer, thoughts?)

Yes. Your unload week is fine.
However depending on your goals Im not so sure Id go 10 8 6.

I am assuming you are refering to core lifts such as bench and squat.

The way I personally like to do it for a max strength cycle which is alot like the way youve done it would be…

week 1 5x5 80%
week 2 6x3 85%
week 3 5,4,3,2,2 80% 82% 85% 90% 92%
week 4 3x3 82-87%

Ive gotten great strength gains doing it this way.