av8- I agree that most times it is total, you know what.
But the problems with the welds is just stress, shear value etc. If you tip over the BX it will crack at the weld (most times). The weld should have the same mechanical properties of the base material if done correctly. If more , you are ok but should not exceed base material in shear strenth.
If less, then your weld size better be correct; Fillets, groove, etc.
There are some many ways to weld, so many materials, that is why they put the warnings on.
I do work in ROP but have work on welds at work and they are a no no here.