How to avoid PRs from auto assigning to Default Buyer

Summary:

PRs shouldn't get assigned to the Default Buyer mentioned in the Configure Procurement Business Function

Content (please ensure you mask any confidential information):

'Default Buyer' is mentioned in the "Configure Procurement Business Function" setup as part of touchless buying configuration for few BPA based PRs. But we don't want to assign all the remaining PRs to the same Buyer, which is also not a good practice. 

We have raised SR 4-0000420169 wherein they confirm that it's the current system behavior referring to below note. But this is not acceptable for the business. Is there any workaround to stop non-BPA PRs from assigning to default Buyer?