At LHR I was very surprised to be asked (at check-in) to weigh my carry-on - Business Class flight. The check-in agent said this was for "Health & Safety reasons as the luggage may fall from the overhead & injure someone"....my bags were overweight. Never had this before & indeed they were borderline aggressive about it, IMHO. Was told I could re-pack my bag (I had 2x bags actually) to ensure each weighed no more than 7kg before boarding the aircraft. I didn't do that & was never challenged again throughout my entire 2 sector journey.
The UK is famous for splitting the responsibility for decisions and the aggressive enforcement of the resulting rules. And you will never meet those who decided, they shield themselves from "feedback" on their decisions. The result is, that many people speak about "the Nazis at LHR".
At another European airport, I literally got told at check-in (when explicitly asking, being largely over the limits, with +5 kg hold luggage and 5 carry-on pieces, in total some 25 kg), "Oh no, for business class, we are very relaxed with these rules". Granted, this was at the early restart of the flights once vaccines became available, though it was pretty explicit by (about) the highest in rank at that out-station. Upfront, I asked by email and got persistent messages reflecting the official guidelines, no mercy. For myself, I thought, this can't be true, the reality will be much more relaxed, and indeed it was.
The low 7 kg is, in my opinion, to avoid discussions for those who show up with 2x 15 kg or so. 10 Kg should not be an issue, is my expectation.