According to the article, and my personal experience, you don't commit directly to trunk. Trunk based means that you don't "collaborate" on a branch. So you write your code based off of trunk, once it's ready you commit in a branch, simply for purpose of code review. It gets reviewed, and probably runs an automated build. Once both pass, you merge and it goes through your deployment pipeline. Yes the merge/code review are manual, but your not merging to say, "I'm ready for this feature to be on prod now" your simply saying it looks good.
The biggest difference is that if developer B wants to use your new method, he has to wait for it to be on trunk rather than branching off of your branch, etc.
It really is the same. He very much could branched off your branch and once merged just start syncing with master. And I see that better than waiting for your PR to be merged.
