The main benefit of having an actual API layer is decoupling - between your front end clients and you back end service(s). This article seems to forget this major point.

Decoupling has loads of benefits - for example, it gives separate development cycles, and in this case provides a point of scalability too - not all REST dbs cache brilliantly or aggressively enough for all use cases.

The point about using delayed syncing between client and server is separate. I can see how it can help in certain use cases (Google docs doesn't auto-save every single letter you type in for example I suspect, but probably bulks them up into a save every x seconds) but at other times this kind of strategy sounds like it will add unnecessary complication.