When creating policies so that different offerings in a request are assigned approval to different Request Managers, the use of the PDA Approval email can approve both, rather than just the offering assigned to a manager. Why?
"PDA" direct approval method is "approve everything you can", which is why this change has been recommended. If you only wish to approve some options, you'll want the other email type, which then sends you to log in to the UI and only approve what you want. Alternatively, remove the Proxy Approval from the role of the managers:
'Catalog -> Configuration -> Request Management Configuration' then remove 'Request Manager' from 'Access Control: Proxy Action'.
Once this has been removed, the user cannot approve on behalf of other users, and so will not do this.