Didn't he play as a CB against Frankfurt last season and the league game after IIRC? I personally prefer him in that position, as he no longer has the pace to track running or the ability to be effective in the final third.
I never said he should be deployed as a CB, I'm just alluding to the fact that he can play there - https://www.transfermarkt.co.uk/marcos-alonso/profil/spieler/112515
He's actually trying to push for a move shortly after signing an extension. It obviously isn't going to happen, but he could kiss goodbye to a starting anytime soon. Azpi, Tomori & even Alonso. We aren't exactly short on options defensively.
They supposedly have first refusal on Kean, so it's a decent chunk of money for someone that has shown very little thus far. Mandzukic/Lukaku deal could turn out to be an odd one, though.
I can't think of the last overseas signing that Spurs made which proved a success. Dybala will definitely have his moments, but I don't expect him to bag 20+ goals like he did in Italy.
I agree that there's no proof and rather a hunch on my part, regardless of how outlandish it might seem. Neither of us will probably ever get a definite answer on the matter.