Are you asking about actually pitching to start PFP drills? Or as Gunner says, pitching to start a team defense drill? Or are you asking that if a pitcher does a side session during practice, does that have an affect on how much overhand throwing they should or should not do during that same practice?What are folks' thoughts on pitchers pitching and making infield throws at the same practice? Volume parameters for either? Frequency?
Are you asking about actually pitching to start PFP drills? Or as Gunner says, pitching to start a team defense drill? Or are you asking that if a pitcher does a side session during practice, does that have an affect on how much overhand throwing they should or should not do during that same practice?
If you just want to be a pitcher and not play anywhere that's fine and you can stay out of infield drills. If you want to pitch and play something else you need to practice there too. If you arm is tired you need to let the coaches know so they can alleviate some of it.