I’ve been meaning to post this since my statement closed. The Citi AT&T Access More card does indeed earn 3X for Samsung Pay gift card purchases, purchases made in the app. I’ve tested and verified this myself.
This goes against the report of Doctor of Credit, but he does only cite one person’s experience. I’ve made sure to verify this against other people’s experiences, so it should work for everyone. This should be especially useful for anyone who wants to buy any of those cards.