There is nothing wrong with allowing the welder during a performance test to back gouge the root of the single sided groove weld (with or without backing) or to rotate the pipe while welding it if the applicable welding standard is FC2002.
Thank the good Lord for FC2002. It has pulled me out of several sticky situations over the years. I find that it is widely used in the Corn Belt and some of Cajon country. From some of the posts I've read here in the Forum I would venture to say it is starting to starting to see wide applications in the oil patch. It really works well with piping systems when there is any question about the welder's skill. As a matter of fact, when I saw those photographs of the welds observed in the RR yard, it reminded me that it is usually easier to get the Engineer to buy the welds off (if you show him FC2002) rather than repairing them.
If you don't have a copy of FC2002, I'm sure it can be located easily if you do a search.
All kidding aside, it amazes me how inventive people can get when they read a welding standard like the D1.X and ASME sections. You have to wonder if they know how to read at all. I guess that is a case where just because one can read, it doesn’t mean they are functionally literate.
The bright side is it is what keeps us gainfully employed.
Best regards - Al