@Mr Sonbir, Thanks for posting in Q&A.
From your description, I know Windows 10 and later feature updates device report not showing in while device added in group.
To clarify the issue, please check the following.
1.Please check the update policy in Intune to see whether it has been applied successfully on targeted device.
2.Are all those devices that were later added to the group not showing up in the report? Do all devices that were previously in the group show up properly in the report?
3.The report data is generated at different times, so there will be reporting data latency, please sync the devices with Intune to speed up the process and check it later.
If there is any update, feel free to contact us.
If the answer is helpful, 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.