Amazing quilt!
Appraisers have their specialties in different areas - that's why AR has the different people giving their expert opinion on the huge variety of items that they encounter. Some quilt/textile appraisers probably have their special niche/time period & style that they are more knowledgeable of.
I imagine if you had a quilt of this age and quality and you wanted to get an independent appraiser you would ask what the appraiser's specialty is ( example - civil war versus art deco) and if they had previous experience with textiles in that time period. Obviously the more experience they have with items made during that time period, the more accurate the appraisal.