> Lastly there's a cost to maintaining a system that doesn’t appear to exist outside of Psalm.

This seems like an odd claim to make (OP also repeats it elsewhere in the text and seems to be aware of a single exception). The analysis described in the blog post is not novel or unique. It is useful but I don't really know what to make of this claim. Abstract interpretation, symbolic execution, and even typechecking systems have all used this kind of approach for many decades. There are hundreds of papers and tools using this approach.

Usually, you'd call this "path sensitive analysis".

I love seeing static analysis show up outside of academic papers, but there is a wealth of material for people to immerse themselves in if they want to learn!