Your initial point was that you disagreed that players have put in transfer requests and then played well. You didn't condition that, you were just skeptical that it happened.
There have been multiple lists of exactly such players who have turned in transfer requests (whatever their reasons and whatever their ability levels may be), had their move refused and then put in an amazing season. You didn't ask whether there were players who put in transfer requests and then still performed well if they were amazing players (ie Kane /Modric/Suarez ) or weren't in exactly the same position as Anthony (Rooney/Zaha) or had a father figure manager (Vieria/Ronaldo) etc etc.
The point with Modric is that he did put in a transfer request,bad mouthed the club, went missing and then still put in an amazing season after and got his move anyway.
Tevez put in his transfer request,got rejected and then knuckled down. They won the league that season. Did something similar that next summer, played only 12 games that season, they won the league that season. Then played 34 PL games the season after, then signed for Juventus for 12 million in the final season of his contract.
From memory, Di Maria never wanted to come to Man Utd and played like it for pretty much the whole time he was here.
N'Dombele is by some distance our worst ever signing. However, he does not belong in this conversation. N'Dombele has been the same since he first arrived, lazy and failing to impress. He put in transfer request not because better clubs were in for him (if only!) but because he wasn't making it here. He was on the market last summer, where the giants of Lyon swooped in on loan....and decided not to take up their purchase option after a mediocre season. He was in the market again this summer, where again the giants of Napoli have taken him in loan, with an option for purchase. The smart money is on us unfortunately being in the same situation again next summer.
None of my comments have been about whether it's smart for Ajax to turn down such a bid (it's clearly an absolutely insane bid). It's been about the pervasive attitude on here by some that if someone is turned down for a transfer request, they just give up and down tools, despite multiple cases to the contrary. Ajax are still a selling club, in fact they sold a player to you literally this window.
If he doesn't get his move and then just gives up and lets his career go the way of Berahino (a player who did let the failure of his transfer affect his future career), he's going to be the party most affected. Not Ajax and not Man Utd. He'd do well to remember that. Carry on, put in another good season and he'll get his move.