If, as according to BLW principles, babies control food and only try to swallow when food is chewed and safe then why, away from the table, are small objects such a choking hazard? Why would they try and swallow a coin but not food that they can't handle?
I don't think it's that definitive in the book is it? I remember it being that with blw they develop the chewing and management before the swallowing rather than vice versa and the argument being that reduces risk . you wouldn't give whole nuts or grapes or cherry tomatoes if you were blw, and there is lots of advice on that kind of thing. Those are more similar to coins etc than most food. They are harder to control and harder to dislodge if they get stuck.
Anything in their mouths is a potential choking hazard - they can aspirate purée as well as choke on a piece of solid food.
What you have to remember is their gag reflex. It's much further forward in their mouths than an adult's, so they will gag and eject any lump that they lose control of and goes backwards. They'll learn to control the food in their mouths with their tongue and then they can swallow when they're ready.