This results in us paying more than is due when they overestimate your usage when the prices fall at the end of the month. So you pay the old/higher price for power you have not even used yet.
Get your own back - instead of letting them massively overestimate your reading on that date - why not give them a massively lower one. As it means you will be saving the potential 10% price drop on all the electricity you have used already.
Don't feel bad about it - they were going to do the opposite to you.