Interestingly enough, his Challah dough recipe, which you can get if you subscribe to his site, doesn’t have any egg in it, though he does use an egg yolk wash. It does have sugar and sunflower oil in it.
One of the items on his Instagram page is a braided loaf that looks like it must be made from a dozen or more strands. (He doesn’t say how many, though he does ask for guesses, so maybe he’ll post the right answer some time.)
No eggs in his dough recipe, but it does have sunflower oil and he uses an egg yolk wash.
There are some vegan challah recipes out there, and one site claims it is OK to use either egg or olive oil, so I guess it is possible to make challah without egg.
I may have to make a small batch of his dough just to see how it feels and what it tastes like. I usually use the challah recipe in BBA, and it is pretty eggy. One thing I’ve noticed when trying to braid it is that the strands will start to puff up again right after they’re rolled out, so by the time you have 8 of them done you’ve got to de-gas them all.