Who was "here several years ago" ? The post I replied to was from the beginning of 2018 (although this thread was started much longer ago than that).
The 3 sisters concept was originally used for growing beans that would be harvested for the dry seeds, winter squash, and field-type corn that would be harvested to grind into corn meal. In other words, everything is basically left to grow until it's mature at the end of the season. That said, there's no reason you can't take advantage of the nitrogen that beans add to the soil to benefit a planting of corn - just use bush or half-runner beans with your sweet corn. My experience with adding squash to the group is that it makes it nearly impossible to get to the corn and beans to harvest them.
