Well...okay, here goes.
Clause 4.2 that seems to be getting attention is "Common Requirements", not "Mandatory", or "Only", but Common. It is also, as other poster quoted, a classification of weld positions. Test assymbly positions are then referenced to 4.3, 4.4, 4.5, & 4.6. As noted by Al, these only have tolerances for any position to vary from the pure according to 4.4 for Pipe or Tubing. Nothing on the plates. If your production welds are going to be in positions as calculated according to Figures 4.1 & 4.2 then the qualifying plates SHALL be in position according to Figures 4.3-6 with no mention of 'tilting' on the figures unless it is tubing.
Now, you actually want to be at Clause 4.18 General under Part C Performance Qualification for welder quals anyway, not clause 4.2 which is only a reference of 'Common' guidelines. At 4.18 we are told "The performance qualification tests required by this code are specifically devised tests to determine a welder's, welding operator's, or tack welder's ability to produce sound welds." And then it goes on to say, "The qualification tests are not intended to be used as guides for welding or tack welding during actual construction." These tests are to prove what the welder can do in ANY circumstance, not what he can do if able to roll a piece to an easier position.
BUT, now let's continue in the Part C section. Look at 4.20 & 21 as well as the entire rest of Part C. 4.21 tells us that the tests SHALL follow a WPS applicable to the test required. Mine is. And it will have a joint detail and all other info as required and specify the tolerances allowable. Notice also the Figures that are referenced for qualification tests. Not 4.3-6, but 4.23-32.
Bottom line: It may be technically correct to allow a slight tilt to a test. But why would I want to? As I already stated, if I am testing for my shop, NO WAY. I want to know what you got. If I am testing for someone else, I have to stand behind the person I just attested to passing, on your behalf, for a welding job. I want to give them and you the best possible assurance that they can do the job.
Now, I cannot go behind another inspector and say that someone is not qualified because they let them weld the plates at an angle. BUT, I won't do it and don't believe it is proper and applicable to our job responsibility. I think the code backs me up on this. I intend to do a little more research on a couple of items. But the tilt is out as far as I am concerned.
Have a Great Day, Brent