Thanks for the information!
While I suppose currently this may be the expected behavior, as there is a limitation:
In meetings with more than 120 participants, the attendance report that's available during the meeting will only include a partial list of attendees.
If you export the list after the meeting, you should see all the attendees without issues.
If you have feedback on this feature, please consider posting in the Teams feedback forum to submit your feedback to Microsoft.
Thanks for your understanding and sorry for the inconvenience caused.
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