Here lies the problem with general residential contractors and their time lines: they always, through no fault of their own, come across unexpected complications/additional work, which makes them behind schedule.
Homeowners typically hire a contractor to do a certain job. Then, when the contractors are there, the homeowners will either add more work to the job order or when the job is being done, the contractor may find additional problems behind walls or in floors that require additional work...which takes more time.
I know. I recently had an old section of my house that was a former summer cottage worked on. I had the old walls removed to the studs. Come to find out, once the interior walls were removed, it needed additional framing, more insulation and some electrical rewiring...which took more time. Then, after seeing all the new walls and windows, the old floor looked horrible, so I had a new oak floor installed....more time. You get the idea.
So, yes, it is normal for contractors and handymen to have their schedules blown out of the water due to unexpected and unplanned work that needs to be done before the job can be buttoned up.