Insurance carriers using outside vendors to determine a vehicle's value seems to be pretty common, although I do not know if it is a "state requirement" or not. I would want to have a copy of the adjuster's worksheet showing how they presented your unit as to equipment, condition, etc to make sure it accurately reflected your TT. Most of these databases are extensive and should be fairly accurate. You can also check the internet for retail prices on similar trailers as a cross check.
2011 Jayflight 23FB G2
2003 Chevy 1500 4x4
Wife Peggy and 2 Beagles and a rescue Cocker Spaniel
2007 Yamaha Grizzly 400 ATV and Yamaha 2000 watt Genny
Me/retired insurance claims and DW/retired RN.
"If the women don't find you handsome, they should at least find you handy."-Red Green