When I was very little (5/6) my first Judo club also had a reasonable focus on ground work and we'd spend about 20-30% of the time focusing on it.
Part of that might have been because we were so young, in retrospect. I don't think it's all that uncommon though I can see why its not the best way
to do things Judo style. Meh groundwork is a serious gap in my arsenal and I need to spend more time in BJJ schools.