Call it being dropped call it having competition for games, there are 6 elite games a weekend ergo 3 elite refs will not get a sl game. And if you only have 6 full time refs like last year 1 gets injured then you have no redundancy and end up having to use lower tier less well prepared refs.
If guys are not performing to expected standard they may well end up doing champ games but that would mean grade 1 ref getting lesser games which then becomes counter productive. Ideally the sport should have full time officials that could cover all pro games but evening we had that experience and ability would differ depending on the individual