I train at an overcrowded dojo, so I don't personally care that a large percentage stays to 4th kyu and injures out, mostly because they never figured out on their own how to roll without hurting their shoulders. But a smaller dojo is definitely going to have retention problems if it doesn't actively teach ukemi as a part of class, and those issues could be with men or women.
I'm a woman and I was taught to fall by men, and have male ukemi role models and do just fine, so I don't think this is about women having a different center of gravity or whatever. But women do differ from men in two important ways:
1. Women are socialized to assume that the problem with their ukemi is innate (my neck is too short, my thighs are too fat, my ukemi isn't very good...), whereas men are socialized to assume that they can troubleshoot and fix problems like this (I can fix my computer and I can fix the way I fall...)
2. Women are more risk averse, generally, then men. If a man falls badly a few times, he learns from each bad fall how to fall better. Women prefer to withdraw from things that hurt them. I learned how to do better breakfalls by figuring out how not to land on my kidneys, but I am not feminine in this way.
Ukemi drills in class would really help both of these specific feminine mindsets. I used to be a sculpture teacher, and found that I could never get my female students to use the table saw. But when I created a short assignment that involved everyone using the saw, and explained how to do it safely, then it became a non-issue and of course the women were often safer and had better judgment at it then the men.
As to the testing thing, nobody on this forum can tell whether you are ready or not, but you should generally test for yourself and to your own expectations (provided they are high enough). You're acting as a role model no matter your rank.
I've never dealt with some of these "female" problems you speak of. If my ukemi sucks I just assume I'll work it out and proceed as required.
I've actually known one to many men who baby their shoulders when uke. In my experience babying anything guarantees your injury.
One thing men can't comprehend is how much it hurts when some one accidentally kneels on your "side-boob bulge" when doing a seated pin.