Today I tried to make some ugly models. My choice fell on this tutorial. At 5:10 the author spins the vertex. But in my case I got this
I tried to transform this vertex to mesh (don't ask me why, just i'm newbie) but it doesn't help.
All is fine if using Screw modifier but why I can't produce moreover the same result with the Spin tool. It looks so mystically:
Here is my blender file