The appraiser is required under USPAP to report and analyze any agreements, options, leases etc. If the appraiser doesn't have a copy of the agreement, s/he can't analyze and reconcile it to the value conclusion.
A good appraiser isn't going to be swayed by the sales agreement, and most worth their salt will give you a heads up and let you cancel the assignment and pay only what they have into it for time and expenses if the deal is going to go south.