Interesting thread.
I've looked at the Neff web site for maximum connected load, and as ever they (like other manufacturers) are as useful as a chocolate fire grate, unless you want to know how to cook a quiche.
I see from some of the retailers of this hob (as others have said), suggesting a connected load of 10800 watts. With diversity, (OP the diversity formula has worked pretty well up till now), that's suggests to me a total current of just over 21amp (assuming no socket outlet in cooker control), have I got that figure correct, members?
OP, reading Neff's glossy brochure on their kitchen appliances, specifically induction hobs, it praises the attributes of it's product;
'Induction hobs are extremely energy efficient, saving you money on your electricity bills. Only the base of the pan heats up, so only the precise amount of energy you need is ever used'.
If diversity was not applied, then the calculation for 10800 watts, would be something like 47amps (even too much for your 10mm perhaps). If you had an electric shower (where diversity cannot be applied), how would you feel about one of your siblings taking a shower for two hours (the time it takes me to cook a cordon bleu meal for her indoors
)? Now this hob is very unlikely to be
'extremely energy efficient' pulling 10800 watts, for two hours, would it.
Whilst I'm no manufacturer of induction hobs, I suspect if you turned on every hob to max, each would cyclic on and off very often and very quickly, therefore unlikely to draw full connected load of 10800 watts.
I would suggest, to put your mind at rest, and take up the offer of having the hob monitored with a clamp meter. Either that, or you go through the pain of having your new flooring ripped and the subsequent mess, to installed a replacement cable, that's probably unnecessary.
Just my opinion. That's about 4 - 4 now