Hello Caesar III.

I think that SIF for a fabricated 45 degree Tee(Pipe to pipe connection by welding) will be much different from a wrought(mainly wrought) Tee.
I don't know as how to differentiate between the SIF based on method of construction.

Also, I don't know if Mr. Becht's explanation has been explicitly added in the code since I don't find any reference for Mr. Becht's statement.

Waiting for response from Moderators Richard and Dave.

Thanks