Lasors is not a legal document and neither for that matter is CAP804.
They are CAA opinion and until tested in court are only guidance.
Lasors was in some ways a wish list for certain people of the CAA and was out rightly ignored by several senior examiners.
As an example the IMC recommended minimums were tested down to the IR mins by quite a few. And there was absolutely nothing the CAA could do if an IMC rated pilot regularly few to IR mins.
So unless your quotes are from the ANO they are pretty much meaningless.
In the old days the CAA used to give written answers. These days they won't. Mainly because there is only one place the law can be decided. There main ploy is to get people to plead guilty and then and only then do they go through the courts. The CAA doesn't have a very good success rate in court and well they know it.
They know fine this practise has been going on for years, they don't like it but there is no safety case to stop it with a legislation change.
As such under the old ANO there was no problem whats so ever doing the 3 as sole manipulator with someone else as PIC who is a none instructor.
How that's changed now part FCL is included in the ANO I don't have a clue.