Sounds like a straightforward time-space tradeoff: if you have the compressed layers sitting around when you need them, you can avoid the expense and time of compressing them.
It still bothers me that the fastest most performant computer I have access to is almost always my laptop, and that by a considerable margin.
Someone should do some lz4 vs. ssd benchmarks across hardware to make my argument more solid and the boundaries clear.
But yes on the extreme end absolutely there's a point where lz4 stops making sense, but also most of us aren't trying to max out a 128 core postgres server or whatever.
Also looking at block-based content store so that blocks can be deduped across images.
Old docker discarded the compressed bits but kept some metadata about the the so it can at least recreate the tar.
It also recreated the manifest o push.
(As others said, compression is deterministic for the same algorithm, parameters and input data)
Tar isn't related here though, we're talking about compression not archival formats