About all I can say about this is that I feel all organic matter is beneficial to the soil. Be it beans or weeds, I don't think it makes any difference. Any weeds can be considered mulch, and it is going to take a while for it to be converted to plant food. It will be of more benefit to next years crops after the microbes have their way with it.Also, there's a nagging question in my mind that perhaps the "weeds" you hoe and mulch with might be putting entirely different set of nutrients back in the soil that the squash/pumpkins need, that replacing them with bush bean "hay" -- so to speak -- may, in fact, be not as beneficial....
I like to do soil amendments in the fall. Add leaves and manure then till it all in along with what is left of the garden plants. My philosophy is to put more on than I take off. Some call this sheet composting.
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I'm like what? SO I go out there and an errant vine has gone through the fence, they do that you know. But there is a cucumber (a big one) that has grown into and through the wood pile. Half outside the pile half inside. They kind of go where they want. 
You had to look fast or you wouldn't have seen it.
Oh, DEFINITELY stop at Ozark Lady's so we can help her out with all that milk.... 
. Although, I'm wondering if heavy additions of compost and some sulfur couldn't fix that 