WRC 297, Paragraph 1.0:

"This Bulletin is a Supplement to Welding Research Council (WRC) Bulletin 107 and is specifically applicable to cylindrical nozzles in cylindrical vessels. As such, stresses in the nozzle at the juncture with the vessel that were not covered by WRC Bulletin 107 can be calculated."

It doesn't get much plainer than that. WRC 107 focuses on the local stresses in the vessel. WRC 297 extends this to consider stresses in the nozzle.

WRC also extends the D/T and d/D ranges and considers the effects of the nozzle neck thickness.