For everyone's benefit, here is the response / resolution to this issue that I got from Microsoft:
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This is a bot used for Dial In Conferencing. It’s the one in charge of announcing when a participant joins or leaves a meeting among other functions. There are other bots that might join calls when recording, enabling meeting transcript and other activities. Usually bots don’t show up as participants in the meeting since they join as hidden. But I’ve seen it once in a while. So while having the bot join the meeting is normal, it’s not expected for it to show as a participant. If you continue to see this behavior please go ahead and open a support incident.
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