Firstly it is important to understand how and when you might be able to delete a Purchase Request (PR) in FinOps.
FinOps only allows deleting a PR when it's in one of the following Status' :
Pending - All users with access to the PR type can delete these.
Rejected - Only users with the correct security permission can delete this type of PR.
Reopened - Only users with the correct security permission can delete this type of PR.
Cancelled - Only users with the correct security permission can delete this type of PR.
If the PR has already been posted to Access Financials, it has therefore become linked to a PO, then you would only be able to delete the PR when the PO is still Pending as nothing has been processed.
If you have managed to delete a PR in FinOps, but noticed the PO remains outstanding in Access Financials then it is probably because either:
The Status of the PR in FinOps was such that it allows deletion.
The User had the correct Security Permission to delete the PR based on it's Status.
The linked PO in Access Financials had not been processed yet and therefore was Pending in the Outstanding Orders in Access Financials.
It is relatively easy and straight forward to simply delete the unwanted Purchase Orders from the Access Financials application with a user with the correct permissions.
Note: There is also an option within FinOps Administrator to delete a batched PO when a PR which has been linked, is deleted in FinOps (this would be a setting for your Administrator to make and can be applied separately to each PR type setup in FinOps).