Who decides an aircraft's maintenance schedule?
The manufacturer lists all maintenance that should be done, and when. This is the first document you found, from Boeing. Some of this maintenance may be required, other things might be recommended.

The operator can use that plan, while following maintenance laws (e.g. the required annual inspection). Or, they can submit a new rolling maintenance plan to their National Aviation Authority (e.g. FAA) for approval, which is usually done to prevent large downtime events for the aircraft. (This "rolling inspection" is done so that all of the necessary things are inspected at the proper intervals, but not all at the same time.)

There's a bit more, too: the Aviation Authorities can create Airworthiness Directives that can add additional required maintenance that must be done within certain limits (usually hourly, but can be situation dependent) for the aircraft to be airworthy.