I like the ideas of this hypothesis, especially considering all of the salt deposits in the Permian. Another theory for Geologists to go have fun with.
Actually the sea is the source of one of the theories of the mass extinction of 65 million years ago. There is a lot of methane locked up in the ocean floors and the theory is that something caused a mass release.
Personally I don’t buy it but I also don’t buy the asteroid impact as a reason for the extinction either. (at least not by itself)