Hi
The exact intention of this paragraph (4.10.1.1) has been debated on this forum before. Do a search to see some more opinions and interpretations. My interpretation is that 4.10.1.1 is included to give guidance on how to qualify corner or T-joints, same as there is guidance given on how to qualify fillet welds. In short, the requirement here is to qualify corner and T-joints using butt joints. (So that you can get the relevant test samples out. - Bends, tensiles etc.) You then need to use the same groove configuration on the test coupon. So, for example, if you are using a double bevel groove for your T-joint, then perform your butt test coupon with this configuration also.
This needs to be read in conjuction with Table 4.5, which gives ranges qualified for further requirements. (Especially look at variables 31 - 34)
Hope this helps.
Regards
Niekie