a money saving pain in the a**
They were meant to be economical, often called a thrift cooker, the well had heavily insulated sides, and the pot had a heavily insulated lid. This meant you could cook one pot meals using less current, and heating the house less ( very important in pre air conditioner days).
I used to have a 1939 GE with a deep well and a deep well cookbook, that stated an entire meal for 4 could be cooked I the average deep well pot, including meat vegetables and dessert. It was full of such recipes, telling one when to put in the meat, then how much later to add each vegetable, and whether the vegetables should be loose or in bundle of aluminum foil, and last when to add a small pan of some sort of dessert, which made for a tightly packed deep well and no second helpings.
Deep wells were economical, and were much cooler to use in pre air conditioned homes, being so well insulated they could be used as a small oven in the summer.
Unfortunately the simply were not as versatile as a surface level burner. It was frustrating when cooking a regular meal to need that 4th burner, for a small pan or a large frying pan, but it is only available for use with a large pot.
Manufacturers tried offering triangular insert pans with allowed 3 vegetable to cook at once seperately, half moon inserts for 2 vegetables, a pressure cooker variant, and even as you see, the burner on some could be raised for use as a surface burner.
However they finally fell out of fashion, being more of a hindrance than a help, and eliminating the possibility of a second 8 inch burner, as well as not being able to be used as a surface unit on most models. Ugh, you should try cleaning one if something has the misfortune to boil over into the well, yuck. And difficult! I don't miss mine.