in addition to what you listed, there's also issue with ownership. you don't own something because a blockchain says you do. you own shares because there's a record of YOU in the company records (they know who to send dividends to, and who to gather votes from to elect the board). most folks own shares in street-name, so the company sees Fidelity (or whoever is your broker) as the "owner"... fidelity passes on dividends, and makes you do proxy voting.
In this case, you're just swapping a regulated broker (like Fidelity, or even Robinhood) for some unknown "broker" who will actually be the "owner", and you really can't do anything outside of that "broker" anyway, with blockchain or not. it's still centralized at that broker level... who will probably get the voting rights (and perhaps dividends?) without the actual risk of paying for the shares Hmm.. I wonder if that's part of the scam (e.g. tokenized shares don't get voting rights, since they're not really "owners"---not sure about dividends----who would the company send the check to?).