Was playing a brawl match and I had 2 Zimone out. One was not legendary due to impostor syndrome. The real had 8 counters on it and the token 3. I attacked as soon as turn began went to reinforce with the reduction since it gave me the option. I had 12 mana 2 mana dorks that tapped for 1 green each and the 11 counters on the Zimones. Since I hadn’t cast an x spell for turn I should have had the reduction. The spell cost was GGX where x=17. With my reductions available and it not being a tap ability or anything like that it should still work even tho it’s attacking. I’ve cast other spells in mid swing to get a boost on Zimone before. Not sure why the reduction wouldn’t apply.