Andy, that’s called “stop drill”, the first time I saw that was an aviation application where a crack in the plexiglass is drilled to keep the crack from propagating. If it’s welded properly, it won’t propagate from that crack, ie, welded all the way through. What will happen, is that it will crack near that area because the metal has been weakened from the welding heat. You could also normalize the area after welding it, but that’s not a guaranty.
A repair for my own pipe I heat the area up with a torch to clean off the inside, let it cool down, run a back purge, set the heat a little hotter on the tig so the weld speed is faster, and zip it up quick….
Everybody has their way of doing things, a manufacturer, doesn’t want to see it come back again….