Here is a bit of Q and A between the maker of the video and a commenter, as well as an explanation of why he did this:

commenter mckenzu (the maker of the video)

I’m aware of the actual name of a Rubens tube, I decided on “flame tube” to make it more accessible for those who aren’t acquainted with the technical name. The whole point of the video is to help make science accessible and exciting. I will add a point in the description about the actual name though.

commenter tanner payne asks:

Couldn’t you just put a piece of straight steel tubing for like 2 inches then put the tubing he has on there so the on ehe has would not melt and it would still work right?

commenter mckenzu (the maker of the video)

The gas connections to the tube can heat up and will melt if you don’t keep an eye on them, limit the use to maybe five minutes at a time unless you find a way to actively cool the connectors down.
For more info check out the blog post in the description.

We hope you enjoyed this cool video!