Think of it like header information. Changing the file compression level resaves the file and creates new header information which will not include the MQA control codes. That information is not preserved.
Thanks. So it’s a tooling issue, right? I guess other changes, like adding metadata, could cause the issue if the file is rewritten. I assume an MQA WAV also store those bits in a custom chunk that could be lost if the tool doesn’t preserve unknown chunks.