I believe your digestive system is altered during the procedure, and the part of your stomach that actually creates digestive enzymes is more or less disabled until you're healed up. But I can tell you it was way different when I had my surgery in 2008. I had to do clear liquids for a few days, and then pretty quickly was able to move on to dairy. Within 2 weeks I was eating creamed cereals--in some cases, literally, pablum-and baby food. That didn't last long because it made me ill.
I sort of freelanced after that. But don't go by my experience. Ask you own dietician. You should have one and if you don't, you should get one who specializes in bariatrics. I was approached in my surgeon's office by a medical student (My hospital was a campus of the University of Washington Medical school) who wanted to study my recovery and did so for seven years. I had to go in at least once a month to let them clock me as I walked up and down the hall, did obstacle courses, had to write down all my foods, had my vitamins and minerals monitored (including about a dozen blood draws, freakin vampires....). Now the procedure is standardized to an extent, but reading this group, I see a lot of small differences from client to client.
Anyway, you can't digest solids, so only clear liquids are allowed for a time. You definitely can't have something resembling liquid food, so no shakes for at least a week or two. I was instructed to make Magic Milk (recipe can be found here using search feature) and in a short time, used that to make smoothies with whey powder from places like Trader Joe's. I also added fruit to my smoothie when it was allowed, but it was totally liquefied.
Now, liquids do turn into solids in the small intestine, creating stool and passing out as waste, but it would be so much worse if you started with solids before the food got to the intestinal track.
It doesn't last that long. I hope you're doing okay. It would be really great for you to do a lot of studying on this topic. It helps a lot.