10 seconds of googling indicates this is true for Windows and Mac as well. I haven't looked specifically, but I'd be a little surprised if it wasn't true for Android and iOS as well.

But really, why would they add rules to prevent people from using certain unicode codepoints in filenames? Should they disallow Klingon as well? Kanji? Of course not. Emojis are codepoints just like U+0061 is.

Of course there are good reasons to disallow things like newlines and forward slashes in Linux filenames, but what specifically would even be the argument for preventing emojis?