I can see the problem with B&Q type "plumbing" joints, although I tend to think that anyone stupid enough to use something like that on their brakes deserves the results if only you could guarantee no-one else was involved
What I can't see is how, unless it's clearly branded as such (which it may have been in this case), anyone can tell by looking at the outside whether internally it's a loose ferrule fitting or two flared joints into a connector block.
Both types are available for high pressure hydraulic use (good for ten thousand PSI or about 680 Bar) and the chance of anyone spotting the difference from the outside is virtually zero.
So, faced with this:
could you tell if it was a Hy-Lok BU (JIS ferrule fitting) or FU (flare type) connector without taking it apart (ok, the x-ray specs view gives it away on this one )?
If anything looking like the above was fitted to a hydraulic brake circuit of a motor vehicle, that would be sufficient to set alarm bells ringing.