Sounds like they are acting according to what their regulations force them to.
Recently had Revolut requiring documentation for source of funds for me, even though 100% of what I have transferred to them came from my own account.
Guess that in my case a red flag was that I used Transferwise to then move it OFF Revolut, using both to withdraw quite a decent amount from ATMs here in Thailand ;-)
I hate this s**t too, literally put it off for a couple of weeks and then had a horrible day trying to get some documents to them - horrible, indecent experience where the︀ reporting directly from the app did not work & all sorts of s**t... Also NOT︁ having standard documents or anything really did not help, half-way expected to get some shares︂ I got with them almost confiscated...
The point is that the cash in my own︃ account could WELL be part of a setup with mules, I've actually seen a couple︄ of westerners in the local mall trying to recruit thai mules - overheard one of︅ them saying something like "and then you just transfer the cash to this account"
Anyway, Revolut did come through with an OK later in the day - so I might︆ keep them as their disposable card is great, other than that most trust is lost︇ in my case.
Just to be clear: in my case 100% of the cash was︈ clean & already taxed ++
This is the new reality: anyone deviating the tiniest bit︉ from the standard behaviour will be regarded as a criminal of sorts, we just have︊ to try to keep emotion out of it & keep filing them whatever papers we︋ can when they ask for them!