I'm not sure what school(s) you came up through or might have in your area, but well over half of the schools in the State of South Carolina would be COMPLETELY unable to field an entire JV team with their 10th grade players - much leass, the LEFTOVERS of 10th grade players.
It takes the COMIBINED 9th and 10th grade classes for most people to make a JV. Some of the larger schools have been fortunate enough to use all the 9th graders on B team, then use 10th graders for JV. However, while this is solid in AAAA, the practice is spotty in the AAA ranks because a lot of them do not field B Teams so they can use the 9th and 10th to make up a JV squad.
I don't know of a single A or AA team with a B team AND a JV team in this state.
From my experience, the 9th grade class is always the largest. They are fresh out of rec league or middle school football and they all feel like they have a legitimate shot at playing. By the end of the 9th grade season, the pecking order starts being established and you have a 20-25% fallout rate of kids who don't return for their Sophomore year. This puts a huge stress on JV nowadays, so many schools send down little-used 11th graders to fill out the rosters.
This whole thing is frustrating and aggravating because of the massive shift in planning and development that coaches had in place for their programs. I do believe, however, that it will settle down and coaches will adapt to it fairly quickly...
...at least... they will if they want to keep their jobs.