If the keywords are part of his legal business name (that which is registered with the state), then the keywords are fine to use. If you're adding keywords into a GBP name that are not his actual business license name, then that's against the rules.
New advertising option:
A review of your product or service posted by a Sterling Sky employee. This will also be shared on the Sterling Sky & LSF Twitter accounts, our Facebook group, LinkedIn, and both newsletters.