So in your understanding of the model, what do you understand to be the origin of the vertical bias which leads to the pressure gradient? Without which there can be no buoyancy.
There are a lot of ways to go into this, let's try the simplest.
As we're explaining Scepti's model, let's go for a good old analogy.
You're in space (no gravity), and you have a perfectly self-contained box filled to the brim with water, and sealed. There is no free space inside it: all of it is filled with water. Equally, there's no difference between the angle you take a reference frame to be: the lack of gravity means that however you look at the box, the forces inside will be the same, so far. It's perfectly symmetrical.
Now, slide in a CD, say. No water escapes the box, there's just now a CD suspended in the middle, displacing some water. Where is the pressure from the water acting?
The box itself isn't really relevant to the analogy, here. Strictly within the box, you have water, and a CD displacing some of it, and exerting force to do so. Does pressure act normal to the disc, or parallel to it?
The experiments didn't go as Sceptictank would have liked so he cried foul. There was nothing actually wrong with them.
Yes I'm absolutely going to listen to your masterful knowledge of denpressure.