No, there isn't.
getColumnMeta()
is still an experimental feature. The actual spec was never designed and the only implementation available is a result of an experiment. The values you get do not mean much since there is no consensus on what they should mean.
JSON is a new type that was added to MySQL, and it was added after the experiment. The type is not present in the code and if needed someone would have to add it, but the question is what should it actually represent. The data you receive in PHP from JSON column type is coming as a string. PHP doesn't have a native JSON type and represents JSON data as a string. You can decode it to an array or an object, but that is the role of the application.