There are two main things that make an appraiser's opinion worth someone actually paying for it: (1) the independence, and (2) the fact that it is based on evidence and logic. Without the evidence and logic, its just another opinion.
Certainly evidence and logic obtained via prior work (i.e. "experience") is part of an appraiser's tool box. But it is the evidence and logic that is the key - not the mere fact that prior work was performed. If the prior work was not performed correctly, or it is not recent enough to still be relevant, then the experience is of little value.
An appraiser might, "based on prior experience" (from many years ago) use a GLA adjustment rate of $40/SF for a condo unit where current data shows should be adjusted at over $200/SF. That is why the evidence and logic must be cited, and not just the notation of prior experience.