With respect you are all missing the point, or, more probably I am making it badly.
A friend of mine was bought a trail lesson for his birthday a few years back. I know he had no intention what so ever of learning to fly. The people who bought him the lesson thought they were buying a pleasure flight. My friend thought he was getting a pleasure flight.
Did he and his friends think the flight would be conducted to the same standard as a commercial operation - who knows, but the CAA would tell them, if it were a pleasure flight, then most certainly it would have been.
The problem is that the regulations exist because the public are entitled to assume legislation is in place to protect them. Now, rightly or wrongly, the CAA obvioulsy believe a diffferent standard needs to be set for a pleasure flight and a trial lesson - that is why the law is written as it is.
On the other hand referring to the other thread on Prune consider how the circumstances differ. Two pilots agree to share a flight to enable the first to collect his aircraft. That is the sole purpose of the flight. The first pilot kindly agrees to give up his time, and the second pilot agrees to pay the cost. Now both pilots are qualified, they understand all about the risks involved in flying light aircraft and are taking a fully informed decision between two consenting and informed adults. On the other hand Jo public who turns up for a pleasure flight masquerading as a trail lesson knows nothing of the risks involved and assumes the CAA is there to protect him. They are neither informed nor perhaps are they consenting to the service they think is being provided.
That is why I think the law is daft!