That is true as long as you can find a chunk of pipe that fits the ammunition you will use.
They claim the chamber can be formed with electro-chemical machining.
Also true. But, if not reamed and polished, a casing will stick in the chamber when fired.
Using the electro-chemical machining, at least one maker reports accuracy approaching that of the ordinary Glock pistol.
Glock follows up with reaming and polishing. electro-chemical machining leaves a rough finish.
While machining isn't strictly necessary, weapons made in that fashion will not have the range or accuracy. The bullet often "key-holes" in the target because they tumble when fired from some of those weapons.
Here is a detailed description of the electro-chemical machining used for Smith & Wesson revolver barrels.
It does not appear that post-processing finishing is necessary.
https://www.firearmsid.com/Feature%20Articles/ecr/electrochemicalrifling.htm