I find in my work that if I were doing a three-commit series like this, I would end up sending in a PR on Thursday, containing all three commits. This is because I can’t be sure the refactor works well until I use the results of it with the new code, for example.
In the scenario I’m talking about, to adapt it to yours, both developers send out their PR or stack on Thursday. Later that day, the refactor commit is approved, but the new API is still under discussion. That discussion takes a full day to get signed off. On Friday, the full PR/stack has been reviewed and all changes are ready to land.
In this scenario, the refactor lands from the stack on Thursday, and the rest lands Friday. In the PR world, both end up landing Friday, because the refactor, as part of the PR, doesn’t land until the whole PR does.