From a end user perspective there should be a third button for reassigning an approval task or otherwise forwarding the mail to a new approver generates a new approval task.
This would be helpful and seamless, especially within an organization, as not everyone is techsavvy enough to utilize the Flow platform, but forwarding an email is straightforward 😄
This is a no-brainer solution - add the reassign button to the email. That has to be the solution since the email is the conduit to the approver to provide reaction, one of which is to reassign the flow task.