Read-only command validation gained additional shell-edge-case detection, especially around zsh recursive evaluation, array subscripts, assignment side effects, redirect expansion, and escaped brace handling. These checks reduce cases where a command that looks harmless can still execute dynamic shell code.
Evidence
Shell safety reasons (search for "zsh $name[expr]", "assignment alters command lookup/execution", and "Redirect target starts with =")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.