Is there data supporting this claim? It seems quite extraordinary that supply would create more demand than it satisfies. That's just not how economics usually works.
If affluent people from around the country are moving to Charlotte, I would think they're likely drawn by other factors, such as their jobs or family roots bringing them there, not by the mere existence of fancy housing and gentrified neighborhoods. If the new development didn't exist, those people would still be moving but would end up choosing slightly lower-end housing -- forcing up the prices and thus forcing out existing residents.
This "making fancy houses only increases home prices" argument seems like a rationalization invented by people who are looking for a reason to block such development. It seems highly unlikely to me that this would actually be true.
Politically, it's easy to be angry at developers for only building high-end housing, when it seems like the real problems are at the low end of the market. However, in reality, you can't expect it to be any other way -- and that's OK, because building high-end homes actually does help the low end of the market too.
New construction is inherently high-end. It's actually hard to build a new house or apartment building that isn't desirable to affluent people -- you'd have to go out of your way to use old design standards and bad materials that don't cost any less but make the home less desirable. This isn't economically viable for developers. So of course developers are always going to target mid-to-high end.
But that's fine, because when you build more high-end housing, then people move up from slightly lesser housing, making that housing available for people to move up to from even lower-end housing, and so on. This eventually makes housing available at the low end of the market for people who couldn't previously afford housing at all -- or perhaps for the government to rent on behalf of homeless people at an acceptable cost.
San Francisco is bizarrely full of terrible 100+-year-old apartments with high-income techies living in them, just because there's nowhere else for them to live. This is a failure. That should be low-end housing, but it's not because there's not enough high-end housing for all the affluent people.