You can only play 10 players at a time. So while hopefully your best players are upperclassmen the rest sit on the sidelines. How is that good for development. Game experience rather than bench experience is a bit more important. Coaches bring up underclassmen to Varsity because mommy and daddy complain and are flabbergasted at the fact that their son is on JV. These parents say things like" he plays for this travel team and I pay this much for training. He should be on Varsity " So coaches bring them up and they ride the pine. That's really a good way to develop talent.
When it comes to goalie play.
This sounds more like 10th and 11th grade parents making excuses for their kids not playing over a 8th/9th grader. If a kid plays on a specific "elite" travel team 9 out of 10 times his is better and deserving. These are just statements from disgruntled parents who think their kid is better just because they are older. If the kids where in the same grade who is the better player.