I suspect the owner/seller is looking for an actual unbiased value opinion to weigh against what the agents' pitch to influence him into signing a listing. If he has a solid unbiased appraisal, and especially if that appraiser clues him in about agents typically anticipating prices going up, rather looking backward to where prices stood 3-6 months ago, seller can make some informed decisions. It may be a tough market to call at this moment because so many ppl have said they feel uncertain about whether the economy & their job will be solid and doing even better within the next 6-12 months, or if they feel things are shakey & unsettled. I've heard most ppl say they are sitting tight and not making any moves until the path ahead is clearer.
That said most Realtors are optimists in most every market, especially when giving a pitch to homeowners, leading them to believe agent X can get higher price than agent Y, but too often, once the ink is dry on the listing contract, listing agents start hammering the Seller for price reductions or sales concessions. So I think it's a good idea to inform prospective sellers of that typical tactic.
Also, just because an excellent appraiser is also a Realtor, those 2 jobs have 2 hats, and marketing and sales know-how may be a separate skill not all appraisers typically have to the same level as Realtors who only do sales 24/7.