>>No one can predict exactly how long any given procedure will take on any specific patient.
Welcome to the real world. Guess what, doctors are not exclusive, many occupations are exactly like that. I used to do Tech Support and now software development. Both have huge variations in how long it takes to actually fix seemingly similar problems. In tech support, I got a couple easy calls which could be fixed in 2-3 minutes, but then a 30-60 minutes hell-call from an old lady with a screwed-up computer. Yet, management fully expected average phone call time to be under 10, preferably 5 minutes.
Same with software development. Some bug fixes can take 5 minutes, some 3 days. Adding a feature has the same variation, from minutes (when all data is available, and you just need to add display field) to days and weeks when the feature is entirely new to the system.
The other occupations manage with the average times set by bean counters. Doctors must as well.
"Informative" up your greedy overpaid "dentist" ass.