In my opinion as the original developer of pristine-tar, it's too
complicated to be usefully used by git. The problem it solves is of a
larger scope than the problem git has here. (I hope.)

Developing pristine-tar did entail much investigation of past changes in
compressor outputs. I know that gzip's output has sometimes not been
deterministic as recently as 2012, see for example
https://git.savannah.gnu.org/cgit/gzip.git/commit/?id=0a284baeaedca68017f46d2646e4

-- 
see shy jo