The early levels are pretty hammered out, but if you find a mistake you can email them at hello@wanikani.com. However, if you’re referring to design decision, then that’s completely a matter of opinion.
They make up their own radicals to make it easier to learn.
There have been many studies showing that ridiculous mnemonics (which is what the radicals are for) are more effective for retention.
This is the same for Kangxi radicals, though…
Wanikani teaches the main meanings, the most important ones. If they were to add every meaning or every way to say a thing, then it would be too much information to take in.
Why, though? It’s not like you’re going to accidentally learn it as Nic Cage. It makes no difference to the average user. Do you think that easter eggs are inherently bad?