Blockchain-free cryptocurrencies are those that use alternative systems in order to function similarly to cryptocurrencies
I don't buy that. I mean people tryed to invent real cryptocurrency since at least 30 years. Noone succed until Bitcoin. There is a reason Bitcoin is worth so much, its true brake-through technology and anything else than that no matter how you call it, its just centralized more or less and issued with central authority more or less thing. Not real crypto.