This is all good info except for the gender thing. The round/long difference is just a growth habit. Watermelon plants (and other cucurbits like squash, zucchini, cantaloupe, etc) produce male and female flowers. Only the female flowers produce fruit and must be pollinated by a male flower to do so.
Probably because beautiful melons had it easy, while the ugly melons had to work on their personality and talent to make up for the shunning they got from the melon community. Big Melon always presents attractive melons on media, making it harder for ugly melons.