Not quite -- the 21 million (or more accurately, 2.1 Quadrillion sat) is a hard line. Any coin not enforcing this rule is not bitcoin. There of course will be forks that dont, but they are not bitcoin.
That’s a definition you can use, sure. And, I do tend to value using words in a consistent way over time.
But definitions are choices. People are free to choose what definitions they think of as “the definition of <x>”. Some such choices are likely to cause more confusion when they interact with others, but this is not always sufficient to discourage/prevent some faction of people from choosing some definition that differs from that used by some other faction.
Under the definition you are using for bitcoin, such a thing would not be the thing that you currently would consider bitcoin. That’s fine.
This doesn’t mean that people wouldn’t use the name “bitcoin” for it.
Perhaps 2000 years from now, the word “bitcoin” will instead refer to apples instead, due to random linguistic drift. (Or, a fruit which resembles apples. Will they technically count as apples, according to our current notion of apples?)
