It’s quite common to have varying valuations. A lot of estate agents come in a bit lower to exceed expectations when it’s sold and some give a big valuation to try and secure the gig (Hamptons are notorious for this) I have always gone with the middle valuation when I’ve sold. And most properties where I live down south always go masses over the guide price, as it’s just a guide not the actual price. As someone said above, the house would be worth what someone is willing to pay

And if they got multiple offers then went to sealed bids, that always pushes up the price. I’ve not read the article so not sure if they did that?