I suggest caution here.

It is up to the landlord to convince the HMCA that they are non resident for tax purposes.

If HMCA discovers that a taxable income earner has not paid what is due they would have the right (and power) to demand payment from you.

I suggest you ask HMCA for their view.

If you have it in writing from them that it is fine to send rent to an overseas landlord that would protect you but from past experience as a landlord I would say that any income from a UK property is taxable no matter where the landlord is living so I think you are being misled