The Saints fans I work with are still pee'd off with Koeman going, this news wll not improve their moods. Tottenham wanted him last summer and failed with several bids. Why they want him when they have Dier and Dembele I'm not sure as I don't see him as being any better then either of them.
It gives them depth though. They play a high intensity game and that is tiring work. Throw in the CL and they will need to rotate more. Makes sense for Tottenham.
The fans would have been more hacked off if he had followed Koeman to Everton so at least that is something.