1) Do you practice techniques from this type of attack at your dojo? A shoulder grab. Kata dori.
2) If so, do you also grab a handful of dogi?
3) Can anyone comment on where this attack comes from?
...I don't like grabbing a handful of gi around the shoulder because I don't like mangling my fingers when they get all crunched up in the fabric. As often as possible, I simply grab the whole shoulder. I think having uke's palm open makes a better channel for entry and connection, but from uke's perspective it is a less effective attack, so it makes the technique less combative.
We do kata dori, but we're an independant dojo so I couldn't say for sure where it came from. The few clips of Chiba sensei
I've seen seem to come pretty close to the form of it I'm familiar with.
We grab a handful of gi; the grab/suppression begins kuzushi and generally sets up a follow-up strike.
As a side note I've seen a couple fights where the shoulder was "grabbed." In one case the shirt just got ripped (attacker had to re-engage); in another it was used to pin the guy against a wall.