FlexyTumblerMom, I have to agree with you on this point and there is a reason to why this happen, in my opinion. I believe at this stage, if the gymnast is on a team, levels 1- 5 more focus is given on Floor exercise, vault and tumbling, I think to hold the interest of the talented tumblers, which caught the attention of coaches in the first place.
But when the gymnast reach level 6, the shift and focus, at least in my daughter's situation had become more intense working on the balance beam and bars routines instead of tumbling, which the practices are long, hard and boring... When the gymnast reach level 6, which they are all still learning compulsory routines in all the gyms, believe it or not, in gymnastic in the levels 1-6 there is a Universal learning Rubric. Everybody are learning the same things and the same routines. But once the gymnast reached level 7 - Optional routine training comes into play and this is where more of the individual gymnast's personality can be developed in the routines... The girls who I spoke to who are still on the gymnastic team that my daughter used to be on, tell us that the practices are more individualized and they are working on all the apparatuses, but are able to focus on the things they enjoy and this is where the tumblers, who stayed are able to focus more on advanced level skills in tumbling like double tucks and layouts, etc...
The hardest part for our cheerleaders who quit at level 6 because of the shift in training they never get to level 7 and experience the advanced tumbling skills that the other girls are learning.
PS: In gymnastic training, half fulls are taught before full and the same with doubles - I was kind of surprise when I saw how tumbling progressions occur in cheerleading, so different.