why will you agree to buy bitcoin from someone directly when you can easily get it through an exchange? the fact that the person does not want to sell it through p2p option but rather wants to sell it to you at a subsidized rate makes it more suspicious and there is no way i am going to buy into such idea.
What is sort of exchanges you implied?
Exchanges can be Centralized Exchanges or Decentralized Exchanges and I know there are many exchanges are there from both CEX and DEX. People have many options to buy or sell their bitcoins, on either CEX or DEX, and if they don't like CEX or DEX - like they are doubtful about whether DEX are truly decentralized and respect user privacy - they can choose to buy and sell bitcoins directly with other people.
Doing this, they will leave no trace online and no trace with bank transfer.