Could you link to where this previous rejection happened? Was it a conversation that happened somewhere where I could read it?
Probably on the mailing list, but a quick search didn't turn it up.
Anyway, do you think that we can safely assume that no other filesystem will interpret these flags differently?
I think so yes, cf. the comments in https://github.com/torvalds/linux/blob/master/include/uapi/linux/fs.h