Do the Beginning Step and Scoring Step happen at the same time, and would triggers from both steps (like Jinx-Loose Cannon and Grove of the God-Willow) go on the same chain?

Ruling: The Beginning Step and Scoring Step happen in order, not at the same time. Effects from these steps go on different chains since they happen separately.

Sequence:

• Beginning Step occurs first and its chain resolves
• Scoring Step occurs second (any hold effects happen after the Begin Step chain has resolved)

Nuances:

• This timing is why temporary units can't hold (they expire before the Scoring Step)