The buyer could pull out regardless of the state in which the buyer is when the offer is put in.
If you put an offer in on a house for the asking price. The agents told you it was off the market, you spend £2k for survey etc, would you be happy that the agent kept marketing the property and if the vendors accepted another higher offer?
My parents once had an offer accepted on a house below the asking price, then a few days later the house was in the paper saying something along the lines of "offers over 80k". Needless to say they didn't pursue the purchase and luckily they hadn't spent any money on a survey yet.