I do not quite understand all the fuss about redefining FE/BE boundaries.

There is one fundamental boundary which makes certain things belong to the backend (unless FE guys get into homomorphic encryption, which I do not believe is on the horizon—though P2P/blockchains are a similar kind of thing).

This is the reason the business domain will live on the backend. And spilling the core business domain over several architectural layers (layers/tiers are understood less strictly) is usually not a good thing.

Technology (with all the abundance of power on the server or client side) will still optimize the bandwidth. This means that, regardless of current fashion, the separation of backend and frontend will try to be done in a way that keeps information exchange minimal.

And here there is a big 'It depends,' which does not have a single answer.