my bad

Sounds similar to the way the GHC typechecker can promote metavariables to the top-level, e.g. when the monomorphism restriction applies. It's then the notion of type variable levels which avoids these promoted metavariables getting unified with skolems from an inner level.

terminal "everything is a dictionary" brain

there being a grammar of patterns, distinct from expressions, was one of the key "woah" moments for me with Haskell; that idea brings so much else into focus

it seems clear he hasn't had that insight (and certainly not experienced pattern matching in a dependently typed language either)