I think that Article 130 9 in
(9) (a) Subject to paragraph (b), a flight shall be deemed to be a private flight if the only valuable consideration given or promised in respect of the flight or the purpose of the flight other than:
(i) valuable consideration specified at paragraph (2)(c); or
(ii) in the case of an aircraft owned in accordance with paragraph (10)(a),
valuable consideration which falls within paragraph (10)(b);
is the payment of the whole or part of the direct costs otherwise payable by the pilot in command by or on behalf of the employer of the pilot in command, or by or on behalf of a body corporate of which the pilot in command is a director, provided that neither the pilot in command nor any other person who is carried is legally obliged, whether under a contract or otherwise, to be carried.
(b) If valuable consideration specified at paragraph (2)(c) is given or promised the provisions of that paragraph shall apply to the flight.
is intended to limit business flying to peoples' own business. To fly in connection with an unrelated business would permit the carriage of unrelated people and freight and the CAA wants to keep a lid on that even if no money changes hands - that's AOC territory and payment often cannot be proven especially if made after the flight.
I don't think there is a need to look for particular logic in this. It's in the same category as the min 5% shareholding in a group owned Private CofA plane. The plane isn't any less safe if a shareholder has only 4% or 0.1%. The CAA make a concession on maintenance, and this is a way to limit how many planes take advantage of it.
I also don't think that Fuji's concern is a problem because with absolutely every business flight there is money or potential money to be made, partly or wholly as a result of the travelling, so if this was a problem the CAA would have to put a blanket ban on all travel connected with a business. Just like car insurers do if you buy a private use only policy.
Article 130 5 is also interesting
(5) (a) For the purposes of paragraph (2)(a), there shall be disregarded any valuable consideration given or promised in respect of a flight or the purpose of a flight by one company to another company which is:
(i) its holding company;
(ii) its subsidiary; or
(iii) another subsidiary of the same holding company.
This appears to make it a private flight if the payment is made between thus related companies. But the pilot still has to be an employee/director of one of them. In practice, in the scenario I described earlier (and which FNG got so wound up about for some reason), the ltd company owning the plane would be a subsidiary of the pilot's main business, and in any case he would be a Director of both of them. Exactly what is wanted here.
I get the feeling that the people I have spoken to years ago about how to do this have actually read through some of this stuff, or paid someone to do it