Have you heard of the Daniel J Morrell? Sank in Lake Huron in 1966, the cause being weak, brittle steel which cracked in a November storm. The story of Dennis Hale, the sole survivor, is pretty intense.
The CG's hatch cover theory was pretty hastily made, due to the first underwater footage of the wreck showing a couple clamps not dogged down. The hatch covers weigh tons, sealed with gaskets. Even with every other clamp dogged, or just the corners clamped, they wont "leak," and certainly not enough to sink a boat.
Curiously though, the first mate on the Anderson reported hearing McSorely yell, "Dont allow nobody on deck!" to someone in the Fitzgerald's pilot house while calling them to give a radar position. Why he would have to tell a bunch of experienced sailors not to go out on deck during that storm means something major must've been happening out there....