An agent will do a cma and come up with the price supported by the market, weather that price is higher or lower than what the seller was hoping for is irrelevant. Since the price that the seller would like to get, or the minimum price they need to sell at has no effect on the price an agent should tell them, there is no point for them to discuss it untill they hire an agent.
A seller would have to discuss the time frame during which they want to sel their house (as that can influence the price somewhat) but it doesn't have to be the first thing they tell an agent. They can wait until they have narrowed the number of agents they would like to work with to 1 or 2 and then tell them the time frame.
I also feel that as an agent going on a listing appointment, it's yoru responsibility to explain to the seller that even though you are talking to them as a disclosed seller's agent, if they do not list with you than there is no contract between you, and should you have a buy who wants to buy their house, you will be working in the buyer's best interest.
At least that's how I feel. Time to clarify this with a broker and see what you are legally supposed to do.