The first link you "cited" talks about state to state migration. Which wouldn't apply to the federal tax rates which AOC is promoting. So scratch that one. It also admits in the article that millionaires do relocate to lower tax havens. When they look at the "world view" the article discusses how many people moved from their place of birth. Which has nothing to do with income taxes.

When millionaires do move, they admittedly tend to favour lower-tax states over higher-tax ones – but only marginally so. Around 15% of interstate millionaire migrations bring a net tax advantage.

The second article also admits to millionaires moving, but then just writes it off as not being a correlation with one sentence and never provides anymore evidence.

The evidence certainly is there. For years, the populations of high-tax states have been shrinking while low-tax states have been gaining residents.But that’s just correlation.

Both of these are terrible upvoted sources, but it's Reddit and people just read the titles instead of the articles.