I have encountered a practice I've seen within two organizations I've worked with, where brand new teams are taught by Agile Coaches that the Scrum Master should calculate/determine the capacity of the Development Team. The Scrum Master should take into account holidays and Paid Time Off when calculating the capacity etc.
More recently, I am questioning this practice because I feel that this something the Development Teams can do on their own because they ideally should be self-organizing.