on the legal side with the banking regulators that's all it is.
the rest is to simplify the likelihood of being part of a department of justice criminal inquiry - not because they did anything wrong, only to prove that they had no part in doing it or having to assist prosecutors and defense. if they just ban customer transactions that don't match their risk matrix, then there isn't data to provide to a prosecutor.
outside of that is the relationship with other banks. basically the underlying financial institutions can arbitrarily cut their peers off or be cut off. like you pointed out.
I'm still drawing a distinction between voluntary "I think I know what I'm doing" compliance and the mandatory compliance that is pretty clear cut.
The result for customers is pretty crappy. None of this anti-money laundering dragnet stuff works and we're the ones burdened with arbitrarily low dollar amount stigmas and limits ($2,000, $10,000) and all the liability. While we occasionally hear about a $2bn decade long money laundering system from a single financial institution dealing drugs with the literal cartel. All to prevent terrorism, which isn't even that expensive. 200,000 9/11's, congratulations everyone. The reality, since apparently nobody actually wants to blow up buildings in the US, is the financial institutions have been tasked with data mining for the state.