[RaisingSpear]

One thing to note is that DEFLATE (underlying algorithm that Gzip uses) doesn't indicate the length of blocks, or make it easy to figure out where they start/end without decoding everything proceeding it. This is likely why pigz can only parallelize compression, but not decompression.

But even if you could identify the block boundaries up front, DEFLATE doesn't reset the LZ77 window on a new block, so corruption could still seep through to the end.