I'm totally for making adults in the lower cats use restricted gear ratios.
Also you do get racing is training, right? Having to spend an hour spinning at 120 rpms makes you a pretty efficient rider, and discourages many lazy tacts you can use when you have senior gears. I always trained on regular gears because it wasn't too hard to hit high enough speeds where my wattage wouldn't match my target, but in any race, even training race, it was always junior gears.