This is based purely on the addresses, from what I see, and it's hard to think what to make of it. If it's purely based on the price, then there were more 'millionaires' when the price was around $50k, $60k, right? In that case, there's no trend to be observed here. But more importantly, it's hard to estimate how many of these addresses belong to individuals and various of them are known to belong to businesses (like crypto exchanges), so they don't reflect the number of millionaires (as individuals having at least $1 million). Also, if it's based purely on the price change, then it means that the distribution of coins isn't really changing, but if it is (and more addresses are crossing a certain threshold in Bitcoin), then it's of more significance.
This is so true! Also, we have to keep in mind that some addresses are lost addresses and will never be recovered, some of them can also be confiscated.
But in bitcoin world, in trading, no one becomes a millionaire out of thin air. When the price is rising, it's like a pool where people put and put a lot of money, then some people start to take the money out of the pool while others are putting and putting. The one who takes the first, is the winner and millionaire. So, if someone become a millionaire by bitcoin, this means that someone also lost money.
What I want to say is that bitcoin is not a magical money printing machine, trading and holding is a game and in game, we can't have winner without loser.