Not likely from a compost pile, squash are very promiscuous and cross breed readily within species. The largest species ( C. pepo)contains everything from ornamental gourds, all summer squash, winter squash and Halloween type pumpkins.

Some cucurbita maxima vars have very hard shell but those I know flesh is not spaghetti type. Sound like an hybrid. Beware compost pile pepos hybrids may be very bitter. Quite inedible.