I have little doubt that they are new bitcoin millionaires and I suspect they are old investors affiliated to several wallets.
Of course, remember not keeping your eggs in one basket? If you remember, it is quite possible for some people to diversify their bitcoin storage in several different wallets.
I believe there are many new millionaires in this industry regardless of the role of the institutions that own lots of bitcoins. Many people have chosen bitcoin as a long term investment asset, store of value and such. But data may not matter because it will only change over time, but of course it makes people more optimistic about bitcoin.
Increasing the number of addresses holding more than $1 million does not give any guarantee that they are new millionaires in bitcoin and I am more sure they are old investors using lots of new storage addresses and there is a reason why they are trying to create lots of new wallets.
Of course, but still address data strongly supports the asumtion that many people choose bitcoin as an investment regardless of whether they are new investors, existing investors, institution wallets, exchange or so on.