I played the Red/White deck in the Starter Duel event. Attacked with 23 token creatures and 1 permanent creature. My opponent blocked some if the attacks but lost after damage. I was able to take a screenshot of this (taken @ 10:07am PST, April 10th). This happened multiple times before in a different games, where I attacked with 15+ creatures (most, but not all, of them tokens) and the opponent either conceded before damage or lost after damage. The Red/White and Blue/Green Starter Duel decks were the only ones used for these cases.

Played on a Mac device (iPad Pro 5th gen, model A2378, iPadOS version 16.3.1)

The expected result was to get the achievement “Going Wide,” which requires “attack with 15 or more creatures in a single combat step.” After several instances of not receiving the achievement despite meeting the criteria, I replayed until I could get a screenshot for proof.