Landing at a grass strip, the pilot has no way of assessing its softness, wetness, or grass length. He has to rely on information given. There's usually no qualification for the person giving this information, other than a radio licence.
I've landed and only on getting out, stepping into standing water under the grass, realized how wet it was. (I did manage to take-off, with mud splattered on top of the wings.) If arriving from a distance, you've no way of knowing how much rain there's been, or how it has drained and evaporated.
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I have heard tell of other pilots raising the flaps to reduce lift and increase weight on wheels and therefore braking action after touch down. Can't comment whether that is a sound methodology though, but presumably drag also helps reduce landing distance?

That sounds like a ' performance' landing, if such a thing exsists? Leaving the flap down ,would as you say, create more drag. Also I am surprised that he raised them on the runway, always taught that was a no no in a retractable aircraft.

Would this have happened if the flight had been carried out by an AOC operator? Who paid?