I think this is grossly exaggerated by marketing. Fedimints do run a consensus algorithm to agree on a global ordering of events and do have an ever-growing database of spent tokens to prevent double spending. This is for all intents and purposes a blockchain, and is even called so in the HBBFT paper.

I think the most useful way to think about it is that Liquid is basically equivalent to one mint, and therefore doesn't scale by itself but does when there's a swarm of those things connected through Lightning. Liquid is great as a real money testbed for covenants, which is useful since you do want to enable covenants on the mainnet.