Hi Ava, thanks for your question.
4-sided welding is done on all 90 degree rail corners and wherever else we can physically reach with our welding equipment. Newly designed assemblies on R and G models include interior panels (versus exterior) and very technical, precision cuts and bends to the aluminum rails. (We are introducing this technique on the S series, too) Experienced welders will recognize that we are not able to "reach" the dramatic mitre cuts on some the new rails, but we do weld accurately and cleanly wherever possible. In additon, we do not weld between a rail and an interior panel on new designs, since this causes creases, bumps, etc., and is not aesthetically pleasing.
Since our newly re-designed rail assemblies have become very popular and they now outsell the 90 degree rails, we will change our literature next year to address the change. Your boat structure, including rail welds, is covered by a lifetime warranty to you as the original owner. We are confident in our work and you can be confident, too.

TB