I think we're talking scientific fact, rather than "common knowledge". This is well understood horticulturally. Weather, nutrient conditions, and inadequate pollination can modify the fruits of a plant. Malformed zucchini show up regularly for these reasons.

As it turns out, Musquee De Provence is moschata, and regular zucchini is pepo, and I believe even regular cross breeding between those two species has been attempted and found to be nearly impossible.

I should add that green zucchinis are known to show parthenocarpic character, where fruiting can take place without regular pollination. The fruit produced have few or no seeds inside.

Perhaps that's the answer. Thanks, Dan.

I managed to find a pretty fascinating research article, where they tried hard to cross different Butternut female flowers (moschata) with Delicata (pepo) male flowers. Rejecting fruits that were simply aborted, they find none (as in zero) fruits that didn't look like Butternuts. Interestingly, ALL of the attempted crosses ended up as parthenocarpic fruit. So if you want fruit, pollinate with whatever. But if you want seeds, you'd better pollinate with the same species. If you want to actually cross the two species, you're just outta luck. I was vaguely aware of this paper, but it took some digging to find it.

https://cucurbit.info/1979/07/attempts-to-cross-cucurbita-moschata-duch-poir-butternut-and-c-pepo-l-delicata/