Can we add bank accounts, delivery method, remittance emails to suppliers at the profile level?

I know how to create external banks accounts and assign them to suppliers but only at the supplier site level using REST API.

I do this by using the external bank accounts API (REST API for Oracle Fusion Cloud Financials - Create an external bank account). Then I use the response from this API once it is successful to take the bank account Id and then I use the instrument assignment assignment API (REST API for Oracle Fusion Cloud Financials - Create a payment instrument assignment) to put the bank account at the site level. But when I try to add the same instrument assignment but instead of the party Id of the site I use the party Id of the supplier, it fails. And when I tried to just use the first API only to create the bank account without the assignment portion, it doesn't appear at the supplier profile for some reason even though it shows that it was successfully created. So I'm not sure what is wrong.