That wouldn't make sense - compression has very cache-friendly access patterns, and would benefit greatly from the observed improvements in memory bandwidth.
That surprises me to hear. I would expect it to jump around in ram a lot. And at higher compression settings, some compressors use a lot of ram, more than will fit in cache.
Compression may be bottlenecked by ram (L2 or L3 cache) access speed, or maybe even dram (main memory) access speed.