You're describing a very unusual behavior since subdomains and email addresses setup within a cPanel shared hosting plan should be specific to the domain name you're setting it up for. It shouldn't be applying the updates to other domains you have aliased to the same plan.
Have you tried reaching out to our live support so our hosting team can help investigate into this activity to see what might be triggering this? It may be hard to address this over a public discussion without having direct access to the plan to review.
If another member has encountered something similar to this behavior before, perhaps they can share what they did to correct it?
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