分かっている and its usage

Question

I was reading a manga and this sentence pops up (the blank space indicates a different speech balloon):

ここは　客が分かっているの大前提の　ツンデレカフェですよ。

For context: the MC enters in a cafe, and he's astonished by the rudeness of a maid, and another maid said this sentence. I know that the -te form of わかる is not used that much, but when I see it, I tend to understand it like "I already understand it" or, in an angrier manner, "I told you that I already understand it, you don't need to tell me!" or something along these lines (similar to ってば construction, 分かったってば!)

Is my understanding correct?

Also, why is the verb 分かっている linked to the noun 大前提 with the の particle? Normally, doesn't a verb directly modify a noun without the use of particles?

Answer 1

That の is a nominalizer and が is omitted after it.

［［客が分かっているの］（が）大前提］の　ツンデレカフェ

分かる is punctual, meaning it refers to an instantaneous change from a state of not understanding to one of understanding. If you are already in the latter state, you should use 分かっている. (Calling this whole thing a て-form is misleading because the て-form of 分かる is only 分かって.)

客が分かるの（が）大前提 would mean the cafe assumes the customers will understand the rudeness of the maids (when they are treated with it). 客が分かっているの（が）大前提 means the cafe assumes the customers already understand they will be treated rudely.

Etymologically speaking, 分かる is the intransitive, and “spontaneous” version of 分ける (“to divide”). Something blurry in your head gets divided and boundaries become clear. In modern Japanese, 分かれる makes up an intransitive-transitive pair with 分ける. This is also punctual (“to divide itself” or “to get divided”), not stative (“to be divided”).