I don’t think it’s deliberately fixed, per se. Rather, I think there’s an informal understanding that it’s better to make Valarr look good – who knows, you might even gain favor with him, a la Kyle the Cat – rather than make him look bad. To quote Hilary Mantel:
“Father, I hope I am not drawn against the king…not that I fear him. But it will be hard work, trying to remember it is him, and also trying to forget it is him, trying your best to get a touch but please God no more than a touch. Suppose I should have the bad lukc to unhorse him? Can you imagine if he came down, and to a novice like me?” (Bring Up the Bodies)
It’s also a metatexual commentary by GRRM on the difference between Valarr and his father, who took on all comers on the lists, who remembers every man he ever crossed lances with no matter how lowly, who truly walks the walk on the code of chivalry. Whereas Valarr is all style and no substance, a bit too privileged and not enough noblesse oblige. And he’s the one who’s remembered as the Young Prince, the hope of the realm after his father’s death…
Suggests a bit of hollowness at the heart of the post-Redgrass Daeron regime, no?