Manufacturer uses self reinforced nozzles contour machined to be butt welded to the shell (Sect. VIII Div.2).
Detail is same as per 2004 Ed. Fig. AD-540.1(a) which doesn't exist in Ed. 2007 of the Code.

Some acceptable details are in Table 4.2.13:
Details from 1 through 4 require inner radius r1 to be from 1/4 to 1/2 of shell thk.
Details 5 and 6 show r1=r2 to be more or equal to the lesser of 1/4 nozzle thk and 19 mm.

Since the inner contour cannot be worked by lathe, being not in the same circumpherence (it follows the cylindrical shape of the shell), manufacturer choses to apply the minimum r1 as from Details 1 through 6: 1/4 of shell thk (which leads to 9 mm radius). There is a good reason for not giving a greater radius, otherwise this was my first answer. Client actually asked 19 mm radius r1. Is the Client right, Code wise?

I believe 9 mm is acceptable because it is not prohibited and there is no mandatory requirement to do otherwise. This is in accordance with "Foreword" <This Code contaains mandatory requirements etc...>
However which is the difference of Details 5 and 6 to justify a different radius?

Comments are welcome
Mauro