I do too (anything@mysubdomain.example.com), but but online services collude with data brokers to share so much information [0] that I don't doubt that many of these "separate" profiles have been aggregated.
Unfortunately the services that supposedly offer to have your personal data removed from data brokers don't seem to support aliasing, so no straightforward way to either find out or have the data removed.
[0] Just look at the scary list of third-party cookies you can't opt out of on Coursera [1], for example:
Match and combine data from other data sources 419 partners can use this feature Always Active
Identify devices based on information transmitted automatically 546 partners can use this feature Always Active
Link different devices 358 partners can use this feature Always Active
Deliver and present advertising and content 582 partners can use this special purpose Always Active