The context here was that it’s not free, as I understood it. So, moving logic to the database, might make it faster, but that doesn’t mean that it’s instantaneous or that I no longer have to think about the scaling concerns of it.
So, personally, I read that section as “logic in the database is not a zero cost abstraction.
Edit: but I was referencing specific performances claims, that you will somehow take some load of database server. I just don't see it.