In an uncontested showdown (when a player moves to an unoccupied battlefield), is the team that moved there still considered an attacker?

Ruling: No, there is no attacker or defender in an uncontested showdown. The attacker and defender designations only exist during combat.

Nuances:

• When a player moves to an unoccupied battlefield, this triggers what is called an "Open Showdown" rather than an uncontested showdown, since all showdowns require Contested status to start
• Even without attacker/defender designations, all players still get an opportunity to play actions and reactions during the showdown
• Players alternate playing actions/reactions when they have focus, with both players needing to pass before resolving each item on the chain