There’s a very long thread about that particular situation here: Can we talk about banned user synonyms, especially for radicals
TL;DR - Radicals which match with a kanji, but use a mnemonic different from their respective kanji meaning are not currently given any love.
It’s actually been brought up a few times, and I’ve also e-mailed the WaniKani team about the disadvantages it brings. Hopefully they’ll actually allow us to start using kanji meanings for such radicals again soon.
Edit: I think I’ll tag the @Mods to let them know that this has come up again, since this is actually the third or fourth time I’ve seen this mentioned on the forums. (I.e., the radical 各 does not allow “each” as a user synonym, even though “each” is the correct meaning for the kanji 各.)