"The heat treatment increases the tensile strength, which in turn allows the builder to use a thinner gauge tube without sacrificing strength"

Sure does, but air hardening steel for TIG is kinda hit and miss as far as that goes. The ultimate home shop heat treating process. These are presumably good alloy choices for the intended process, but I have a hard time believing critical heat treating processes are being left up to the vageries of the TIG arc. It's just a good story. The usual story, which is also nonsense is that welding undermines the frame strength in some significant way. The story here is that welding improves it. Also probably nonsense. It's all part of the long heat wars.