But this is Spurs we are talking about. This deal would be annoying for us or some other top, top European club.
When Christensen went on 2 years loan to Borussia it was great deal for them even if they knew they were going to lose him if he becomes good because he gave them 2 years of good performances.
Real can use this clause in two years, do you think Mourinho cares about season 22/23 now?
Another example is Morata. Same situation, Juve bought him for 20m, he gave them 2 solid years and Real then used buy back clause for 30m to sell him for profit. Alvaro likes Italy and if Juve wanted to keep him and offered him what we did he would stayed there.
If Spurs take Reguilon only on loan for just 1 or 2 seasons it would be still great deal for them because he is miles ahead of what they have. And now we have Covid crises so in two years they would be in much better situation to go and buy new LB.
Also worth mentioning Reguilon wants to be first choice LB in Madrid and if Real decides to take him back just to sell for profit again Spurs would be in poll position.