I would never feed them dry myself even though they say you can. Way too hard. I soak for 12-24hrs depending on my routine at the time. Wouldn't do any less.
I always feed mine well soaked
a) because of the risk of choke
b) when you see how much water they absorb in a bucket, then I assume that if that much water is absorbed from the intestinal tract by dry nuts, then the risk of impaction colic is raised
I think its best to feed all bucket type feeds wet. yesterday my 3 yr old got choke , very mild thankfully. he was eating hi-fi lite and a few hi fibre nuts, i'd not damped it enough. its a very frightening thing to witness and must be awful for the horse. all my feeds will now be soaked from now on, even if its just a handful of chaff.
Grass nuts are fabulous, but we soak ours until they are a mush after having two episodes of choke last year. It was out oldie who bolts her food. Scary and expensive. They don't mind them soaked at all.