2:26 – if the mesh hasn’t been unwrapped why does it still show as if it might have been

Primitive Objects come unwrapped by default, you build up upon it and make a mess out of the original UV’s. All the while you are modeling and changing your mesh and then you unwrap and get the shape in the UV’s your mesh now has. 

UV’s are fairly simple. It’s just as a cornflakes box when you open it up to throw it in the trash. You don’t want the 3D version of the box in the trash, it takes too much space, so you rip the box by the seams to make it flat and 2D. In Blender you are trying to intuitively think where the seams should be, because there are no seams. In the cornflakes box it comes with the seams already, in Blender you have to decide where a cut should be for an object to be lay flat if ripped like the cornflakes box. 

I’d say so yeah. Martin or Adrian can either confirm or deny. Anything they say will be held against them. They have the right to a Blender attorney. 

Confirmed!

All Primitives come with a default UV Map. There is a checkbox in the Last Operation Panel:

I don’t think (but I might be wrong) that you can disable this permanently, though.

@thehomme a little history to help you understand the teachers here. Before 2.80(it may be 2.83) Blender didn’t create UV Maps by default and shader editor defaulted to generate. They’ve been teaching Blender since before 2.70 and have gotten use to explaining things in a certain way. Also before 4.0, blenders default UV Maps are usually pretty bad. We’ll see if the new 4.0 algorithm does a better job. 

Using your analogy, If you have a PNG that has an alpha channel it defaults to total white(full opacity). You can delete the alpha so that the PNG has no alpha channel. You can leave the alpha channel just as it is, but sometime you need to make adjustments to the alpha channel. just like how an alpha channel has to have a value for every pixel of the image, UV Maps must have every vertex, edge, face, vertex normal, split normal(Also known as edge normal), and face normal accounted for in it’s mapping. If you take an image that doesn’t have an alpha channel and then add an alpha channel to it in Photoshop you will get asked do you want to default to full opacity(White) or full alpha(Black) or at least it use too. I haven’t used Photoshop since version 7.0 on windows 98. Gimp just defaults to full opacity. If you add another UV Map or delete the UV Map and add one a default UV Map will be created because you CAN NOT have a blank UV map. Again ALL vertices, edges, faces, vertex normals, split normals, and face normals have to be mapped. 

The info is still in the UV Map’s texture space. Usually as a single point. The UV editor only shows texels to pixel mapping for faces since vertices and edges aren’t rendered in most render engines. Face corners can be moved to a single point thus creating a single texels for an entire face. This is a common atlas work flow. 

***Edited*** this is my understanding of UV Maps. I could be wrong.