That's why I've always been (and still am) uncomfortable with the way that people have to use the right combination of components from different manufacturers, placed inside the enclosure in the right way in order for what they have then assembled to be compliant with a BS.
I started out thinking that that was such a flawed process that whilst a claim that if you did all these things you would be complying with the requirements of BS 5733 would be true, that would not equate to being formally conformant, or certified, or whatever the term is, because of the lack of formal verification. An electrical installation can be done in a way which complies with BS 7671, but formal compliance cannot be claimed without some kind of verification process.
But we are being told that BS 5733 compliance can work that way.
What we have here is the situation where someone can do what the instructions say and simply say "I've made something which complies with BS 5733". It's a very different approach from using, for example, an Ashley J80x. That's an accessory which in and of itself complies with BS 5733 - if you mess up how you use it you may breach BS 7671, you may even contravene a usage requirement of BS 5733, but you will not make the accessory itself non compliant. With a Wagobox etc you do not have anything compliant until you've assembled it. In theory someone inspecting an installation where compliance with 526.3(vi) is a prerequisite for compliance with BS 7671 would have to inspect the Wagobox to verify BS 5733 compliance, which makes a mockery of MF connections not needing to be accessible for inspection.
I don't doubt the sincerity, bona fides, etc of Connexbox, but I am not at all happy that BS 5733 works this way, and statements I made in the past about Wagobox compliance were because I never imagined it could possibly work that way.
You say that people could put anything inside the box, and I strongly agree - I've observed before that one day someone will open up a Wagobox and they will find something other than the right connectors secured in the right way, and I remain fully confident that that is an accurate prediction.