At the moment users can push changes using an email that is not mapped to an Atlassian account.

Users can make changes to their local Git configuration to use a different username and email that is different than their primary Atlassian/Bitbucket Cloud email. If the email used in their local Git configuration is not set as an email alias on Bitbucket Cloud, the commits they push will not be linked to any accounts.

This can appear concerning as it looks like a random individual pushed changes but in actuality, they are an authorized user.