Not sure if this is going to be of any help at all....
I've grown zucchini, squash and pumpkin. I can tell the difference between zucchini and the other two....leaves are a greener colout. But with squash and pumpkin....I can't tell until after several weeks. The squash I grew flowered a lot quicker and once the flower started to bulge into fruit, then I could tell. The pumpkin just put out lots of growth and kept spreading out. Took a while for it to flower.
I took this picture about 3 weeks ago. "This" was growing 'wild'; we had dug in our bokashi bin food scraps here some time ago and this plant just sprang up. I figure it is pumpkin. All it's done in the last 3 weeks is keep growing and spreading.....