This has been in place for many months and will have been subject to gradual phase-in and constant incremental tuning, so nobody will have been able to notice a

This has been in place for many months and will have been subject to gradual phase-in and constant incremental tuning, so nobody will have been able to notice a distinct jump in speed. It's about shaving off the milliseconds and the microseconds. Also, they are just as much interested in the overall throughput at their end as the perceived speed at your end.