I encounter this as a stereotype online with fair frequency. It is probably just because of my personal experience, but I really question it. No one in my gym starts on the knees, and when I was a whitey, starting on my butt seemed awkward, I didn't know what to do, and it made me feel more vulnerable...so I started standing. My gym being full of accommodating people (and pro'lly 'cause I was a girl), the other person would just start down. As such, my top game developed before my bottom game.
Didn't you get swept much? I ask because I generally start from guard against newbies, including female newbies. From there, I'm working on guard retention and sweeps. If I get a sweep, that's when I start working on new submissions, or ones I'm just not very good at.
The guys tend to find ways to improve position after a few sessions, often by just being explosive. Since I'm a big guy, that doesn't usually work for the females. As such, they've always wound up getting better at tucking elbows, protecting their neck, building a frame, etc. This is where the guys might appear to be getting better results (because they're getting out), but the females are actually improving more in terms of technique.
That's just been my experience with every female I've trained with, especially the newcomers since I've been training. They've learned a strong survival game out of necessity, often more technically than their male counterparts. Interesting though to hear how different your experience was.