I feel sorry for the FTB, but it is not uncommon for disappointments when buying a house. My son has just lost out on a house he wanted because he couldn't move as quickly as another buyer, for instance.
Agreeing to sell a house at £valuation minus fees is very different from agreeing to sell at £valuation minus offer significantly above the asking price, too. In the first example the loss isn't real, as it would have gone to the estate agent anyway. The second is a real financial loss, and we can't possibly know whether that is affordable for the seller, who is only in their 40s. We don't know what plans were there for the money, or what other factors are in play.
I agree that it is not your business, OP, unless there is a lot more to this than you are telling us.