I'm not entirely sure what other result people are expecting from the Championship team of the season given the constraint of three players from any one team. Burnley's defensive record was, until recently, allied to relatively poor attacking output so it was the obvious choice for them to provide the goalkeeper and two centre halves. While Leeds' wing backs have been the best in the division by a country mile as well as being a critical part of the team's success, the same can be said for their main wingers (James and Solomon) and Tanaka in the middle of the park. Five into three doesn't go.
That leaves the front 6. Hamer is a shoe-in but beyond him we've not been great going forward; although you could make a case for Tyrese Campbell as a striker given his goals per game but his availability has been limited; Sargent has scored 15 and has played nearly 1,000 minutes more than Campbell. Rightly or wrongly, Sainz basically sewed up a spot with that ridiculous run in the autumn where every long range effort he hit went in and so his recent form (2 goals in 22 appearances) is overlooked.
I'd have gone with: Trafford // Hume - Estève - Egan-Riley - Firpo // Bellingham - Souza - Tanaka // Solomon - Sargent - Hamer
If we're allowed subs (up to 3 per team) then add in Cooper (United), Struijk (Leeds), Bogle (Leeds), Brownhill (Burnley), James (Leeds), Murphy (Portsmouth), Rudoni (Coventry), Campbell (United) & Wright (Coventry). I've probably overlooked a couple of Bristol City players but I've no idea about any of them.
The final, damning, indictment of the current state of English football is that the best team the Championship could put out would finish rock bottom in the top flight.