The word “cob” is used as an English mnemonic for at least 3 different readings.
It’s counter-productive to tell learners “the mnemonic is ‘cob’” if they’ve memorized “こぶ” as the reading for “cob” and now you’re saying it’s “こぼ” or “かべ”. A 1 to 1 mapping would serve users much more effectively, though I’m sure it would make creating the mnemonics more challenging. But really, that’s what WK is for. If everyone was committed to just coming up with their own mnemonics for everything we could all just use Anki.