My indy mechanic does that too. Quoted me a job one time at 5 hours labor that took me three when I decided to do it myself and it was my first time even. I know he uses a program to calculate his quotes and most times that software highly over-estimates. Maybe that's due to guard band to protect against under-estimating.

That software bases estimates on one way of doing the job which usually requires taking out a lot of stuff. It does not take shorts cuts into consideration. That so called 5 hour job, I did not remove half as much stuff the TIS said to and still got it done.

I found a bunch of shortcuts on YouTube. The thing about shortcuts though is you usually don't have as much room to work in versus when removing a ton of stuff.