[Peterweb]

Where have you backed up your iPhone? If using iCloud, that only backs up the app data for apps you select. I believe the backup you have on the MBP is a full backup of the device to use if needed to do a full restore of the iPhone. Others can correct me if I am wrong here.

I see no reason you could not remove the iOS installer if you have already moved your iPhone to 15.x.x.

 

[Peterweb]

That is why I asked where they had made the backup they mention in their post. If they had no other full device backup, they might want to keep the backup on the MBP.