Maybe I am confused about OTC? Bisq sounds more like what you are trying to describe here. On Bisq people list their price for as much bitcoin as they want to sell. This is to avoid KYC AML usually when people do not want to go through the legal rigamarole of a financial services platform.
Discussion
OTC or Over the Counter to my understanding is large quantities being sold “off market” usually between institutions or exchanges and miners. Not the same as p2p but somewhat similar i guess