I've had two episodes with choke, both were older appy geldings that were on beet pulp..the first wasn't my horse, and I was a witness more than anything. The second was my own horse, and I hadn't soaked it at all but he slobbers a lot and was bolting it down.
It was only once and I never fed it dry again.
I don't really soak it, I just add the same VOLUME of water as beet pulp shreds, pour off (to get excess sugars out) and add it again and feed right away. That's not what the instructions call for but it works just fine for me that way. And a side note, I've fed it dry (in small amounts of course !) to my younger horse and he's NEVER had any problems with it. Pelleted form is supposed to be more iffy than just shreds.
There's no proof that beet pulp can cause blockage in the gut, as it mixes with stomach fluids before moving on, it's the throat that's a problem because the throat isn't designed to "fill up" like the stomach is. Most Senior feeds contain dry beet pulp in the pellets and yet they can be fed dry safely.
My boy when he choked started pawing the ground and looking at his stomach-I really thought he it was colic. Then he yawed his mouth and tried to cough. I felt the big wad in his neck then. I ran a hose in his mouth and flushed it out while massaging his neck. Took about 15 minutes to get it all out, but as soon as he spat it out, he started eating again, like nothing had happened.
Not something I worry too much about happening again though. I wonder if older horses tend to have more problems with it due to flacid muscle tone in the neck? Or just a coincidence.