AASHTO's "Standard specifications for structural supports for highway signs, luminaires, and traffic signals" shows that it should be detailed with a PJP groove weld with fillet overlay (with unequal legs) in the commentary. See below from the commentary:
It would be nice if they knew the fundamentals of welding symbols. I believe AWS A2.4:2020 is the latest revision. The welding symbols shown by the sketch is so wrong in so many ways.
It isn't the standard at fault, it's the detailers that don't take the time to read and understand what it says. The sad part is that the standard is mostly pictures, almost like a comic book.
My experience has been that the reinforcing flange to the pole is a CJP bevel groove weld with a reinforcing fillet. The volume of the flange is equal to the volume of metal removed from the pole.
I am surprised to hear you say that your experience is that it is a CJP and not a PJP, I often see hand holes at mid height of poles (next to light brackets mounted at mid height) where it would be very difficult or impossible to get any backing in place - at the base it may be a bit more doable, depending on the size of the mast. While certified welders that can weld full pen without backing may be commonplace in the petrochemical industry, it is pretty unheard of in the utility industry.