Quick spot weld question

Hey all, go to Tim McAmis Perfofmance Parts: Floor Strips. Watch this video. He has lots of great tutorial videos on youtube.
From back in the 70s, I remember my Mechanical Engineer friend telling that a straight weld would create a structure more prone to cracking. He would create weld joints just like in this video.

I`d weld it up using the spot technique , and weld the new connectors to the floor pan too = stiffness !
Body flexing is what broke them loose to start with.