It "conflicts" in the same way noscript[1] and script "conflict" no? They're basically related features, but can't really be made exclusive because the mere act of trying to do so wouldn't work: as the link indicates, executing code in a !module browser reserves the type (requires a specific set of types) so you can't use that as a way to opt in !module browsers.
[1] an other fun element with wonky parsing rules besides