It seems that several GS1 MOs are requesting their own GUDID (US FDA UDI regulatory database) accounts, is this practice part of the FDA policy?

The only organizations that are allowed to have a GUDID account are the labellers. GS1 MOs should not apply for a GUDID account as this is outside of FDA policy.

GDSN Data Pools would only have an Electronic Submission Gateway (ESG) account, this also applies to third party data providers (such as PTC and Reed Tech among others) contracted by the labelers to register data in the GUDID. If a labeler is going to submit data to the GUDID using a machine-to-machine message, SPL, without a third party, they will also need an ESG account.