Never encountered any. Not even watermelons.

They seem to be suggesting that triploid watermelons are parthenocarpic

Here is a link that might be useful: triploid watermelon

Triploids are not. That is why you have to interplant pollenizers with seedless watermelons.

I know. I don't quite understand that article's point. I wish they would develop them for just that reason. Gardeners with limited space don't want to devote a whole vine's worth of ground to a pollinator they don't want to eat.

But what I can't understand is the failure/inability/indifference to developing a parthenocarpic cucumis melon.

Three years later, any difference? I haven't seen any parthenocarpics besides cukes. I'm working on my 2018 list....

There are several varieties of parthenocarpic zucchini . Have not found anything else, seems to be limited to cukes and zukes at the moment.