1 Hour rated exterior wall on Single Family House

I have an odd situation in Washington State and was hoping someone here might be able to give me some insight. I have a house that is framed and ready for drywall and the inspector found that the property line jogs and thus a portion of the exterior wall is closer than 5' to the property line. Thus the inspector wants the GC to do a 1 hour rated exterior wall. I found U356 which meets the criteria (in my opinion) but the inspector is having issues with several aspects. One aspect is that the test is for 2x4 studs and we have 2x6 studs but it is my understanding that an INCREASE in size is allowed in UL tests so I think that is okay. The wall is composed of hardi siding, plywood sheathing, 1/2" gyp bd, the stud and insulation. I am proposing we provide 5/8" type X gyp board on the interior to basically meet U356.

Given that a stud wall with 5/8" gyp bd each side is a 1 hour rated assembly this wall in theory is easily a 1 hour rated assembly but there won't be a test that collaborates that.

How much leeway do inspectors give in situations such as this. There is no way I am going to find a tested assembly that meets the exact field conditions and tear down of the house seems a bit overkill for a slight overlap of a portion of the exterior wall on the setback.

What options does my client have here?