Why is ActiveRecord::ConnectionAdapters::*#native_database_types not a class constant?

It looks to me like it should be
ActiveRecord::ConnectionAdapters::*#NativeDatabaseTypes

It looks to me like it should be
ActiveRecord::ConnectionAdapters::*#NativeDatabaseTypes

I wouldn't assume that there's any particular reason there, but if I
were guessing I'd say it was to make it easier to work with in
subclasses.