Yes, I considered that - it could be a coding error (ie hotel does not accept reservations so the message pops up). It hasn't always come up, though.

(Didn't the old London Wembley property also not give points? Again, though, whilst Hilton managed that was not branded as Hilton.)

If there are no other obvious examples of this practice, then let's assume it is a bug for now.

It is also possible, of course, that the hotel is owned by the same people who own the Westin and the 2nd Meridien in Dubai, both of which refuse to take part in SPG .....