Disallowing these case/underscore variants from referring to differing values could be quite ok -- even a plus-- if (but only if) an additional rule is added to disallow any variations of the declaration-time casing for a variable within the same scope to prevent the need for bespoke grepping tools and discourage arbitrary variations. If that restriction was added one could argue that this improves code readability (& "listenability") by have fewer variable names available in the same scope which would sound the same but aren't.
Even with such a rule, you would still run into problems if you want to grep for a token that's used in some application but declared in a separate library.
