The video quickly runs through a couple of weirdnesses with Cylinder Unwrapping. It is more a demo than a tutorial, but it yet contains some hopefully useful information for your daily work.
This is a quick glance at unwrapping.
Add a cylinder and keep the cap ends open.
The result is a circular shape. Why that ?
of the model also adjacent in the UV map.
it does not contain any seams.
let us now create a simple test pattern.
Go to image, new image. Also check UV test grid.
Open the properties sidebar in the 3D view.
go to object mode and inspect the cylinder surface.
So, there is no seam as expected, but the test pattern shows distortions.
Well, actually we want to map the cylinder to a flat rectangular surface.
Lets try this by adding a seam.
Now select all vertices and unwrap again.
although we still see a mismatch at the seam.
We can do that better by using a cylinder unwrap.
The unwrap should work smoothly because we indeed have a perfect cylinder here.
unwrap, then select Cylinder projection.
and only the vertical scaling seams broken.
the cylinder is 3.14 times larger than its height.
Lets ignore this for a moment and lets check one other annoyance.
The UV map is not exactly aligned to the texture bounds.
While this is not important in practice, nevertheless it is unexpected.
Here is a trick to fix that.
then Zoom into your model.
and move the entire object a tiny bit to the left.
And now the UV map aligns perfectly.
I do not know why that happens, but it works.
Now scale your cylinder down a bit.
unwrap again. I expected that the UV Map would keep the same.
but the scaling on the Y axis is changed.
UV, transform, scale to bounds.
Now scale the cylinder up.
unwrap again. Is that expected behaviour?
Well i personally did not expect that to happen.
to get around some pitfalls with texturing.