@mortstar is right. From the data we’ve seen, onboard monitoring can have significant errors, either underreporting over reporting depending on manufacturing tolerances or errors e.g given two identical heat pumps one may be significantly over-reporting COP and the other may be underreporting, unfortunately there’s no way of knowing unless you can compare with a MID meter.
See this thread for examples:
It’s usually safe to assume that the electricity is monitored correctly, the error is usually in the heat measurement.