His point is that reading is about the journey not the destination. Better to read less books but savour and enjoy them (or if non-fiction is your thing take the time to learn the materials properly) then finish them to say you finished them.
As someone whose greatest pleasure is a day off with a good book, it's hard to balance reading with all the grownup responsibilities we have, and as a leisure item, it's usually the first thing cut from a busy day's schedule. Reading a book a week isn't as much about the number, but by gamifying the outcome, you prioritize it above things you might otherwise not.