he sure is in a hurry.

It's fairly common, called an economy bowl or bowl from  board. If possible, it's nice to knock the corners off before mounting on the lathe but if not, that's okay too.

 

https://www.youtube.com/results?search_query=economy+bowl

 

Steve

I have a Ringmaster bought from widow of a turner. As Steve posted it can be done on the lathe but as I understand it is not easy. You have to get the angle correct or you will have great difficulties sanding the bowl after glueup. Even at that sanding is not as simple as sanding a turned bowl and takes patience because you will spend a long time with 36 to 50 grit to get the ridges out. Not impossible but the whole task requires patience to get there. 

    I think these were originally done on bandsaw or scroll saw. I notice on the first two videos they do not show angles to cut the rings and discovering that will help a lot.

FWIW I use a circle cutting jig on the bandsaw then take to the lathe.  While the circle is not perfect it is much closer than turning the square, especially on larger stuff.

I made one... It uses round solid carbide cutters.