That's very informative and what I also experienced in Germany for example.American cyclist here. While Apple Maps directions aren't technically wrong...they are still really poor for cyclists when compared to Google Maps. Here's an obvious example, where Google Maps understands what is a very popular path for bicyclists that goes along the Mississippi River here in Minneapolis. It's hands down the safest and most scenic way to get to this destination. Apple Maps follows that same bike path for a short distance, than inexplicably detours off of it for a bike lane that is longer, more dangerous, and far less scenic. My best guess is that they are only aware of bike paths that are directly adjacent to, or shared with, roads.
I think Google Maps has better tracking of cyclist data (GPS) and the fact that they handle elevation, car density (if cycle lanes are shared) + traffic lights / pedestrian density. The algorithm seems to work better than AM.