I do not speak for the staff or the gym at all, just my impression of events. But if athletes are placed on a team with a certain set of skills, or with the clear intent that they will develop and maintain a certain set of skills that are the basic requirements of the level and the needs of the team and stop doing them, or do not develop them a staff does not have the right after making it clear all year what expectations are for the team and what they must be met to compete at Worlds to change personel around. My suspicion is that a lot of gyms make that choice early on and continue to do so during the year, stacking high profile teams preferentially from the first of the year, while others do their best to "spread the talent" to give every team their best chance during the year and athletes the opportunity to grow into their position. I'm not suggesting there will be wholesale changes on any team, that would be suicide for that team.
In my opinion, there is nothing wrong with defining again the skills that were evident at tryouts as Worlds teams move into the final stages of preparation and if a few are moved around by the staff due to the needs of the team so be it. I think teams routinely replace athletes that are not "up to snuff" during the year, and that has not happened on any team that I have seen this year at our gym except for injury. I strongly suspect that if the athletes recommit to the skills they had early on, and the conditioning to perform them, there will be little or no changes. However, these are my impressions alone, I do not speak for the staff at all, but I know that the staff has notified the kids it is time to step up or they will do what needs to be done to make the teams most successful. That is the appropriate thing to do for the vast majority of athletes that have made the committment to keep and develop skills and conditioning. If it is not "fair" to change an athlete that is not performing up to expectations, then it is not fair to the rest of the kids that are doing all that is expected plus some only to be penalized by those not performing. At the level these kids are competing the alternative is to not give them a chance. My experience is that the possibilty of that happening tends to invigorate all to recommit to what is needed.
