[1718627440]

But this would result in showing double newlines, when you view a CRLF file with an LF viewer, that also interprets CR. This does sound more like the file would have only CRs, which is what classic Mac did pre-Darwin. But that doesn't make any sense.

Maybe Notepad is actually saving LF, but marks the file as CRLF and some WSL translation layer then triggers and removes LF, because they are not CRLF?