No! The funds are not in your custody since you can't access them freely without a second-party agreement on it!
It's a false sense of security but it's the same thing when looking at the final decision, the only difference between this and the CEX is that the CEX can't move your funds without you accepting but at the same time, from your point of view you can't recover those funds without a third party accept either.
You cannot expect to be in full control of the wallet all through a trade with a second party who is expected to send you the first value of the bitcoins in the wallet and then trust that you will send them after confirming the transaction. But there is a lot of difference between giving up custody to an exchange, which can at anytine and at their discretion restrict your access to the funds and entering a contractual agreement with a trader to protect both parties.
That is not a false sense of security.
So no, you're not in control!
Being in control of funds means you can move them at any time in any fraction of the total sum as you desire, not happening in the above scenario.
As said above, you're in a trade with a second party, it's unrealistic to expect full custody every step of the way.
A huge difference between;
• Not your keys at all, and.
• Holding half of the keys.