Today's Random Question: "...The Musical"

Why do some shows have "...The Musical" in the title of their name in their official posters and marketing, while some don't? Is there a standard or protocol that dictates it, or is it just a whim of the producer and/or creative team and what they feel like? AVENUE Q, CHICAGO, and KINKY BOOTS are some that have The Musical, while HAIRSPRAY and THE BOOK OF MORMON are just that and no subtitle.

Then there's HAMILTON: An American Musical, PIPPIN: The Broadway Musical, and COME FROM AWAY: A New Musical.

Why the differences for the same type of product?

What I really don't understand is when they add "The Musical" onto titles that never had that in the first place when they are revived. I have never recalled "Once On This Island" being "Once On This Island: The Musical" until this revival (I guess that's similar to the Chicago example). Didn't they tack that on for the current production or am I simply not remembering the original correctly?

An even better question is when shows use "A New Musical", how long does it take until its no longer "new"...