that's what they tell you....All sealing pliers will have an identification number on them that marks the seal with that number. It’s for future reference when something goes wrong they know who was last at the job. Sometimes if the sealing pliers are not on correctly the number won’t show.
Unfortunately a laptop can be hooked up to a keypad meter and tell when the magnet went on and off and how many units went through the meter while the magnet was on.
I've a mate who's a spark & says it's impossible to tell what's being used in any house without a reading. hence the need for a reading at least once a year.
& also why they're busting to put in smart meters which can tell individually.
not that I would advocate such blatant abuse of the plastic framed boxes still in use in for eg my house...