@MDM Admin Thanks for posting in our Q&A.
For this issue, most bulk actions support up to 100 devices. For the rename action about iOS/iPadOS devices, it only supports iOS/iPadOS supervised devices with iOS 9.3 and later.
https://learn.microsoft.com/en-us/mem/intune/remote-actions/device-rename
If the device is not in supervised mode, it will not list under bulk action.
Hope it will help.
If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.