Greetings-
I followed the steps to a tee and at 4:44 of “Marking Seams,” my layout in the lower left UVEditor window is different. Everything prior is exactly the same. I repeated the lesson multiple times to ensure nothing was missed. I had to rotate the sections to match the layout.
I did see a similar issue with the UV islands and I did in fact apply the scale in Object mode (Ctrl + A, scale)
Welcome to this site.
Show us what you get as a result.
If you only mean the UV was rotated but still correctly shaped I doubt you have a problem. Every file has some differences and Blender effectively guesses how to lay the UVs out, that is why UV editing is important, to make them work for you and your textures.
General Q&A note
Help us all to help you.
Please give full screenshots with any questions. With the relevant panels open.
Also, include the lecture time and name/number that is relevant to the problem/issue.
This can be done by Blender itself, via the ‘Window’ menu bar top left hand side.
On that menu drop down is ‘save screenshot’.