I don't quite follow your train of logic there. 5.2.3.1 refers to a written training program, while 5.2.4 refers to alternative welding qualification methods. The methods in 5.2.4 are alternative for the welder qualification in 5.2.3(b). When 5.2.4 does apply is when the welder was qualified to weld by testing on production parts that were radiographed (a), the PQR that was used to qualify the procedure (b), or qualification in accordance with other specifications where the qualification also meets the S9074-AQ-GIB-010/248 requirements. These don't have to do with the training and written test program in 5.2.3.1. So in essence you are correct that paragraph 5.2.3.1 is mandatory, but it doesn't have anything to do with 5.2.4.