You would be better served by looking at Table 4.8. I am looking at AWS D1.1-2000, that's what I have handy.
Looking at Table 4.8, on the left column look down to to find the tested position 3G in the box marked Plate - Grooves. Reading across the table you see that you are qualified for butt joints, both CJP and PJP, if the pipe is over 24 inches in diameter (note 4). However, if you are welding a T, Y, or K joint, you are not qualified for any CJP joints, only PJP and fillets for both pipe and box tubulars (read notes 5, 6, and 9 for additional restrictions).
As for a tube to a plate, I believe that falls under T, Y, and K connections. Its a CJP weld, so the answer is no, they are not qualified.
A butt groove weld would be two lengths of pipe or tubing placed end to end.
Good luck - Al
