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Something wrong happened with the Grassy Terrain duration here! It seems the terrain countdown shown in Showdown was erroneous, it apparently lasted six turns.
https://replay.pokemonshowdown.com/gen8vgc2022-1511394703-nc7t30bcvhd6dri0f4h8y47ip394h7zpw
BUG STATUS: CONFIRMED - MECHANICS (SERVER)...
I just tested it out on the Switch. Fire Pledge worked normally and attacked without waiting for the Grass Pledge-based Max Overgrowth. So it seems it actually is a Showdown bug. Please, admins! Thank you in advance!
Is this normal? Turn 4: when using Fire Pledge with Charizard and Max Overgrowth (base move Grass Pledge) with Venusaur, Fire Pledge does actually wait for the Grass Pledge combo and does no damage.
https://replay.pokemonshowdown.com/gen8vgc2020-1085242989