In this case, I beg to differ.
If, in the experience of the Connector of this meter to this ELCB, they considered it to be useless in this environment, based upon their professional opinion or not, then it could be reasonably assumed that if connected to the mains supply, the user of the property/equipment is unprotected against minimum risk.
So the person making that connection to the mains electricity is in a position to 'reasonably forsee harm' and they become liable under the Duty of Care laws.
Let's say I'm doing a spot of plumbing and I discover there's a voltage across the pipes. Now I'm not responsible for electrics so, as not my responsibility, I say nothing to the householder. However I can clearly 'forsee harm' and so have a Duty of Care to inform the householder and recommend that the mains be immediately isolated until the source can be investigated. I should note this on my paperwork and have it signed off as advice, in order to cover my ass!
Duty of care to the 3rd [ and subsequent ] parties is the basis of negligence.
As a plumber, I'm supposed to test a whole central heating system, if I swap out 1 valve. The rest of the system I never touched [is not my responsibility...] but I'm supposed to pressure test it - so I was taught. Of course, 99.9% of plumbers will only test the swapped-out bit and it's immediate surrounds & go on their way!