When the client changes their email from "Your profile" in WHMCS 8.1, no 'verification' is done on their new Email.
In WHMCS 7.X, when the user changes email, the new email is considered as 'unverified' and it needs to be verified.
Upon contacting the WHMCS support team, they said:
For e-mail verification, it takes into account the e-mail address on the Client themselves - it doesn't consider the login User. Therefore if you change the e-mail address on the User itself, it won't affect the e-mail verification status show on the client area (usually the "Your Profile" page).
I request WHMCS to verify email when changed in "Your profile" page like it was in WHMCS 7.x because this is important too.
WHMCS Team Clarification:
This request is about maintaining synchronization between the Account email address and User email address, if there is a 1:1 relationship (ie. the Account is associated with just one User who is the Owner, not associated with any other Accounts). Updating the User or Account email address would also update the value at the other location, either via a prompt to the user or automatically.
This would then trigger the verification of the Owner User's new email address, and in turn potentially simply account management for those who don't need multiple Users.