Implicitly indicated compression is also a "feature" of LZJB which we've used for firmware update files. Figuring out what was going on and fixing the issue when a bootloader suddenly started rejecting new firmware updates was interesting and annoying.
The updates were processed in chunks, and rarely a chunk doesn't compress at all - which means that it took a long time before it happened the first time. Always fun to find issues with code that has "always" worked and suddenly doesn't any longer.