Crazy, right?
I would expect vocabs used in the context sentences should be in wanikani at some point. And I was confused because I already learned the kanji for big, but not this vocab.
Technically it is not one word but two: 大きい + 過ぎる. The latter is called an auxiliary verb, and they can be combined with other words, like you see in this example. In Jisho, entry #6 explains its usage:
This is a super-common phenomenon, so it is worth knowing about it.
As to why it is not in WK, please keep in mind that the vocab words are mainly there to reinforce the kanji readings, not to teach vocab as such. The readings are already covered with WaniKani / Vocabulary / 大きい and WaniKani / Vocabulary / 過ぎる .
Yeah, WaniKani has many words that can be used as auxiliaries, like 始める (to begin) or 終わる (to end), but not every combo you can make with them, which is… Pretty much with every verb. There are about 30 verbs that can work like that in Japanese, attaching to stuff to modify the main word.
It’s worth noting in addition to @NicoleIsEnough comment that WK doesn’t teach any grammar. So you’ll have to get used to seeing unfamiliar grammar like 〜すぎる.
OP, you should make sure you’re doing grammar study as well and then these won’t make you doubt yourself as much!
You can use ~すぎる with any adjective or verb, so it seems like you’d end up with a situation where WK needs to contain 大きすぎる、小さすぎる、良すぎる、悪すぎる、綺麗すぎる、痩せすぎる、太すぎる、食べすぎる、眠すぎる、働きすぎる、勉強しすぎる、知りすぎる、分かりすぎる・・・ pretty much ad infinitum
I think it’s weirder how they sometimes do include words that are really just inflections of another word. For example, 呼ぶ and 呼ばれる come to my mind that are two separate vocabulary items on WaniKani even though it’s just one word
And in the lower levels they also include adjective turned into noun, like 高さ and 長さ, as well as plenty of する verb like 確認する even though they are obvious grammatically. I guess they try to strike a balance of having a few very useful inflection as vocab for beginners without overloading the vocab with just inflection for everything
Though that’s one you’ll even see in monolingual dictionaries as a separate entries, because it has at least one meaning that can’t be explained merely as a conjugation of 呼ぶ, which is “to be treated to a meal.” If you look up 呼ぶ, you won’t find “to treat someone to a meal” as a definition, but for 呼ばれる you can find “to be treated to a meal.”
WaniKani doesn’t teach that meaning… but dictionaries are at least consistent, that they usually only tend to give entries to things that truly deserve them.