Last I heard (~5 years ago), lambda@edge doesn't actually run on edge POPs anyway; they're just hooks that you can put in your edge configs that execute logic in the nearest region before/after running your edge config. But it's definitely a datacenter round-trip to invoke them.

Adding that much compute to an edge POP is a big lift; even firecracker gets heavy at scale. And security risk for executing arbitrary code since these POPs don't have near the physical security of a datacenter, small scale makes more vulnerable to timing attacks, etc.