Or at least it seems so....
I happened to catch the toilet cistern not quite fully emptying one time with the lid removed. When I have watched it previously, it always seemed to fully empty. Further watching proved it was quite variable as to how much water it dumped down the flush pipe, so as the old plastic flush unit was 30 years old, I decided just to fit a new one - as I already had one in the plumbing spares. A Dudley Turbo 88 9".
In the process of trying to get that out, the old float valve brass arm snapped, it was ready for snapping anyway, by the looks of it, so back to my plumbing stock to see if I had any float valves. I found a Dudley Hydroflo Quiet fill, and fitted that, but it was awfully slow filling, until I read the instructions and twigged to the fact that they came with a removable flow restrictor installed. Once that was removed (we don't have that much pressure), it filled very rapidly indeed.
The flush is better now, than it has ever been in the 30 years since it was first installed, it also refills much more rapidly than it ever did on the old brass ball valve.