I watch a bit of their stuff, he is one of the first names on team sheet, is always involved, is contributing heavily (goals & assists) and in a lot of games his assists numbers would be a lot higher if they had better forwards. I would agree, he is one of their better players.
That said, feels like classic levels, is he killing it in Championship? yes, would he be at least a decent lower level PL player? yes, is he something more than a squad/bench option for Spurs? unlikely.
If we got 15M+ for him, cash in, move on.
I do think it's another nod to recruiting, the players we buy now, even if they don't work out for us, are decent.