Existence of a minority currently doesn't negate the strife it passed through when those minority numbers were much bigger. Which still exist in regions where the numbers swing the other way - kashmir.
"Indigenous sub-cultures who share many similarities" doesn't mean "cultures are the same". All their current scripts originating from the same Brahmi script is part of that shared culture.
Your example of multiculturalism is more in line to the indigenous cultures throughout EU/Europe sharing similarities. While the context of European discussion on multiculturalism is on migrants and their culture.
"Indigenous sub-cultures who share many similarities" doesn't mean "cultures are the same". All their current scripts originating from the same Brahmi script is part of that shared culture.
Your example of multiculturalism is more in line to the indigenous cultures throughout EU/Europe sharing similarities. While the context of European discussion on multiculturalism is on migrants and their culture.