Yes they are counted as individuals. They are the owners, it’s just that when they use middlemen, those middlemen can do something about that ownership. In a similar way, people own their house in a particular country, and that country can still do something about that ownership. In the case of Bitcoin, the exchange losing or gambling away your coins still makes you a creditor in their bankruptcy, which means even if you lose the money, there is some kind of ownership claim.

If a graphic shows 80% of all bitcoin is held by a handful of people, all it does is give ammo to people who don’t understand the nuances. We already see this happen with the tables of addresses per wealth bracket. This particular graphic focuses on how much different categories are invested in Bitcoin, which is what people are mostly interested in. Everyone already knows much is held at exchanges.

On your final note, cold storage is not a requirement for individual ownership. You can own bitcoin non-custodially in a hot wallet.