How to make attachments flow to the email buyer receives when PO is approved?

Summary:

We have a requisition where we set the attachment category to "To Buyer" and attachments flow to the PO. However, these attachments are not included in the email that the buyer receives when their PO is approved - only the PO pdf is included in the email. We would think that if the attachment category is set "To Buyer" then the attachments would flow to the email the buyer receives alongside the PO pdf. Can someone confirm if this is expected functionality? It is not related to max file size as we confirmed that already and we tried turning on