Drawbacks of using Command based autonomous.

Why did team254 not use WPILIB’s command based autonomous structure?

Secondary question: How to calculate time step for Pathfinder using this structure?

Command-based requires you to make certain assumptions, and depend on the nuances of someone else’s implementation. If you prefer to not make those assumptions, you can do it yourself.

Timer.getFPGATimestamp() is one way to get the current time. Simply counting main loop calls and knowing the expected call rate is another. Both have their drawbacks and advantages.