These things happen in the industry and it’s quite common, but the only thing that matters is all of them sorting things out and working effectively to give a good quality product.
As long as the person in doing what is asked to do and the team agrees I would have no problem as a PM to let him go on a small vacation.
If a certain team member has any obligation with the other as a PM I need to know both sides of the story and talk it through with the people involved as communication is the key if you are working in a team.