Van der Poel also seems far more willing to loose to Pogacar than to anyone else (especially van Aert).
This might be a similar situation to de Vlaeminck/Merckx. Roger talks *** about every rider, except for Merckx who he touts as best ever because it is undeniable that he was a better overall rider as they rode at the same time.
By praising and loosing/sometimes winning against the best of all time (Merckx for de Vlaeminck and Pogacar for MvdP), he increases his own legend and has an argument to be the second best overall rider. (And this works, I see many people that believe him to be better than Evenepoel or Vingegaard which I disagree with)