I think that's not required anymore since libraries v2.0 allowing for dependencies.
Don't manually import the secondary libraries and leave that to the primary library's library.properties file.
Update:
Paul, I've just now seen your GitHub reply - now I understand what you mean, but I think it'd be less hassle for users of the lib if they didn't have to think of importing secondary libraries they're not using themselves and as long a previous version works with the primary lib no need to update.
If the update is "required" to remove the warings just up the dependency to pull in - only my 2cent.