That's exactly right! The argument is that if you look at truly reliable cloud services (think Google). They already use consensus protocols to replicate the database globally for fault tolerance purposes. The spanner paper does a decent job explaining their architecture.
https://static.googleusercontent.com/media/research.google.c...Why not do it for decentralization purposes too?
Blockchains are just a another class of consensus protocols. IMO one of the defining aspects of blockchains is the stronger threat model. Traditional consensus protocols are designed to be crash-fault tolerant, not byzantine-fault tolerant.
I wouldn't get tripped up by the word "validator". In the academic world we probably would have used the term "node" or "replica". It has a special meaning in the blockchain world because it conveys a sense of trust and work-checking.
"Who pays" is a fantastic question. The blog completely elides the question about incentives which in my opinion will vary depending on the app. For creating an censorship-resistant Wikipedia, it'll be different than a communications app. Hoping to write a blog post about that soon after we get more built to show.