It's HIGHLY unusual to go through level 7-10 at one level per year unless you're elite tracked. 8 and 9 are frequently repeated. There's definitely nothing wrong with that the OP's coaches are saying for the average JO non elite training program type of hours and commitment. Also, if you competed the beam routine you described at level 8, you would be hit with big deductions because it violates the difficulty restrictions for that level (they can do one C acro skill). But really, this goes back to coachp's post in that only the skills matter and not what the level is called. It's frequently better to repeat a level in order to train the technique of the next skills without the pressure of rushing to compete them and then getting fears, injuries, poor technique. So, we agree about that.
I stand corrected on the beam..I think the preference is for BHS/BLO but some compete a BT instead if they don't have that series. We had a L8 state and regional beam champ this season, I just watched her routine on YT. She competed BHS/BLO and a RO/Full dismount. (maybe the full is a "b"?) But my point was, it's not unheard of to compete upgraded skills when they are clean. Our gym claims this is why they have above-average success getting athletes all the way to L9 and L10.
Kipper's gym had 6 L10's compete at the state meet (I just looked) All but one scored 36 - 38, so they are "true" L10. The only one who repeated a level getting there transferred from a different gym after her first year of L9. There are 2 others who did not compete at state due to injury, but neither of them repeated L7-9 either. So I would say at her gym, it is not "highly unusual". Nothing wrong with repeating a level when it's warranted, and I would say that looking at all programs across the US, repeating is the norm. Kipper's gym does have repeaters..but they also have several who are one-year-per-level, and a few who skip levels.
So, my point to the OP was, the fact that her gym repeats L9 without exception seemed odd to me. They NEVER had anyone do a single year of L9. The statement wasn't that it's infrequent to do a single year, but they NEVER do a single year. Compared to a gym that I KNOW produces Div 1 athletes routinely where L9 is rarely repeated. There are some gyms in our area who have lots of L7-L9 repeaters, but they rarely have anyone reach L10 with full 10.0 start values, and almost never have athletes go on to NCAA gym. If her dd's goal is college gym, it just made me wonder enough to ask the question. If her dd is at a gym where almost everyone does 2 years at 8, then repeats 9 until they quit or graduate, she is not likely to meet her goal, even if she has the talent. I just wanted to raise the question.
@gymdog You're welcome to PM me for gym details.

We can still agree that it's the skills that matter more than the level, and competing where you are comfortable and successful is much more important than rushing to L10.