It would be my understanding that the effeciency (E from UG-27) would be = 1 (for the tube side only), since there is no welding on the cric. and long. "seams" (no welding of a head), thus the seamless vessel section does not need to meet the UW-12(d) requirements. (The shell side circ. seam would meet the applicable UW effeciency.)
My concerns would be if anyone could interpret this any other way, or if there would be any exceptions.