I'm going to go back and dig down on what I tried to convey above.
"Why is heavy referee curation (in the way of 'tailoring play' and 'spotlight dissemination') a problem for 'Challenge-Based-Play?"
Consider sports competition. Lets go with basketball as most are familiar with that.
A referee has enforced the ruleset neutrally through the first 3 quarters. The outcome of that neutral enforcement is that team x is up by 20 points on team y and the game isn't remotely in the balance. In fact, its basically over.
Deciding that it would be better for team y and for viewership if the game was still in the balance, the referee begins tailoring their adjudication of events (and disseminating spotlight as a byproduct) such that team y cuts the lead in half with 8 minutes left to play. With 4 minutes left to play its a 2 possession game. Perhaps they start adjudicating the always difficult "block/charge" call in favor of team y. Maybe they let team y get away with more physical (illegal) defense, which leads to turnovers and failed offensive possessions for team x. Maybe they start calling more soft fouls on team x.
Viewership re-engages.
Team y feels good about things as does their fans.
Team x (and team x's fans)? Not so much.
And, most relevant to our discussion, the actual competitive integrity, the actual emergent property of the authenticity of two forces colliding and getting to find out which prevails...that is all damaged irreparably...due to the signal of referee intervention.
THAT is why "tailoring of play" and "spotlight dissemination" are completely dysfunctional with the sort of Challenge-Based-Gaming that @Campbell is invoking. The apex priority of play is rendered obsolete.
Challenge-Based-Gaming does't possess the apex play priority of "tell a fun, collective story with a lead-storyteller who adjudicates toward the most/best fun." Hopefully fun emerges out of play as a byproduct...but the primary aim is the satisfaction of finding out who wins/overcomes (team PC or team Obstacles) in a competitive environment.
And who wins/overcomes doesn't just mean the players. It also means finding out who wins/overcomes amidst the PCs and what to make of those PCs after they win/lose, overcome/relent. If a GM and the table wants to find out if PC x overcomes their addiction or falls ever deeper beyond the point of return...then no punches can be pulled by the GM...no tailoring of play. The only thing that the GM can do is frame the situation, play the adversity, and play by the rules until we find out if we have a story of absolution, redemption, or a story of crushing loss.
It is 100% possible to have a "Challenge Based Gaming" experience in a game that features heavy DM adjudication. "Challenge Based Gaming" was the hallmark of Classic D&D (OD&D, B/X, etc) before the game became more formalized with precise rules.
The DM doesn't have to enforce only just the ruleset. The DM can enforce the ruleset plus their own modifications and rulings that achieve the game they want as long as they do so consistently and fairly.
That apex priority of play can be achieved in other ways than just neutrally following the ruleset.