OTC trading is something like independently exchange of your assets without any interference of middle man.
you're talking about
peer-to-peer trading.
OTC trading is done directly between two parties and can be peer-to-peer, but it usually involves a broker who brokers the deal and acts as custodian and/or central counterparty.
when people say OTC, they usually mean
off-exchange, meaning it doesn't affect spot exchange prices or order books.
What is the use? is there a legit platform for OTC trades.
in the bitcoin world, OTC trading desks are often run by exchanges. bitfinex has an OTC trading desk. so does kraken, itBit and several others. the primary reason to trade OTC is to fill large order blocks without slippage and without moving the price.