Like someone else mentioned: you should be able to join meetings without an account.
That said, making an account with a custom email address will not create a microsoft mail inbox for you. Microsoft, however, will use your email address to send service-related messages. If I recall correctly, you can manage what kind of messages you want to receive, in your account settings.
The main difference is that you’d just be making a regular(free) microsoft account bound to an existing email address of your choice, as opposed to binding your domain name to a microsoft account to host your email there - which is mostly something companies do and is a paid service last time I checked.
My theory is that it covers dash cam recordings (video and/or audio). Some dash cameras point backwards from the back mirror, so they get a partial view from inside the car. Everyone's assuming that Nissan is intending to collect this info, but their EULA might merely be a side-effect of dash cam data being available to technicians when they work on the car (e.g. fixing the dash cam).