I may have posted this photo elsewhere, but here is a classic example of crossed squash. On the left a Hubbard, on the right a Banana, and in the middle a cross of the two. The seed of the cross was saved last season from a Hubbard. I had the two maximas growing last year.
You can save seed from squash and it will usually grow, but unless you can isolate it from other varieties of the same species, you never know what it will produce. This is why it is a risk to save seed from any squash you buy at a store or market, as you can't tell what it was grown close to. It is likely a cross if the farmer had more than one variety in his fields. Some tell me it takes over half a mile from other squash to really be isolated as the bees will fly up to a mile easily, and the nature of bees is to be pretty species loyal. IOW a bee working squash will only work squash.
I have only been growing one C. moschata, the Butternut, and I save seeds from those. They come true to form.
I grew several pepos and maximas this year, so the only seed I am saving is the Butternut again.
I had to pay a premium for maxima pumpkin seeds this spring. Next year, I am tempted to just grow one maxima, the pumpkin, and plan on selling the seeds.
Now I am torn, because it may be better to go for the Red Kuri. It seems many seed places are out of stock on that one.