The COOP proposal clearly defines the Cross-Origin-Opener-Policy HTTP response header as a non-structured-header with exactly three valid values. However, @domenic has recently observed:

I just kind of thought we were not creating any new non-structured headers. (And, it'd be pretty weird if COOP was one thing and COEP another.)

I can't speak to the first observation, but parity with COEP does seem valuable. Since the parsing rules for COEP are currently in flux, I wanted to see if a similar change should be considered for COOP.