Essentially, yes.
Both buyer and seller deposit their security deposits and the bitcoin being traded to a 2-of-2 multi-sig escrow, where they each hold a single key. Once the fiat payment has been made by the buyer and confirmed by the seller, they both agree to release the bitcoin to the buyer, and to return both security deposits to the relevant parties. In the rare case of a dispute, there is a timelocked transaction signed by both parties on creation of the 2-of-2 escrow which sends all the coins to the Bisq DAO for arbitration, but it is very rare that this is implemented.
Understood, how about fiat transactions though if one decides to cash out or buy in? Online bank transfer, mobile wallet transfer, that's when it gets tricky since that's essentially a direct transfer between both the buyer and seller.
On a centralized exchange, the seller's crypto are escrowed. Buyer goes first by directly remitting the cash into the seller's bank account, so seller receives the money but wants to pull a fast one, buyer raises a dispute.
Mediator (support rep) comes in, checks both sides of the story and finds that seller is trying to scam. Releases crypto to buyer, suspends/ bans the seller.
On decentralized exchanges, I can't imagine that happening without some sort of third-party intervention.