What is the bug? The /learn command tells me that all of these moves can indeed be compatible on Tangrowth, both currently and in Gen. 7.Bug report -- Tangrowth Egg Moves
Egg moves in question:
Powerswap (swap ATK / SpA changes with target)
Leaf Storm
Swagger
Egg Chain instructions: Using Pokemon Heartgold
>Male Espeon lv78 with power swap
>Female Seedot / Nuzleaf / Shiftry
>Male Seedot with powerswap.
>Lv Male Seedot with powerswap to lv48 keeping swagger, evolve him into shiftry learning leafstorm at lv50
>Male Shiftry with Powerswap / Leaf Storm / Swagger + Female Tangela
>Tangela with Powerswap / Leaf Storm / Swagger
>Heart Scale to teach Tangela Ancientpower, lv up evolve to Tangrowth.
>Now Tangrowth with Leaf Storm / Powerswap / Swagger + any TM / HM / LvUp / Move Tutorable move.