Yes you would add multivitamins/minerals if they don't have them, and oil/fat. The Absorb contains all these except the fat and iron( because some with IBD can't tolerate iron).
If you eat no fibre or solid food at all you get liquid stools. You can avoid that if you eat some kind of veg also or drink something like psyllium.
Actually the Absorb+ sounds like it has much less fructose in, looks like they reduced it since I used it.