Chaotic Swell doesn't prevent effect of stadium while discarding stadium

It shouldn’t let the effect to happen before being discarded. I think that this is a bug.

● Put [Parallel City (BKT 145)] to Hand

● Mazeman has shuffled deck.

● Chaotic Swell (CEC 187) will be discarded as Parallel City (BKT 145) is played.

● Chaotic Swell (CEC 187) was discarded

● Parallel City: Any damage done by attacks from Mazeman’s [G], [R], or [W] Pokémon is reduced by 20 (before applying Weakness and Resistance).

● Parallel City: Dreamcast can’t have more than 3 Benched Pokémon.

● Emolga (TEU 46) was discarded

● Parallel City is now in play.

● Parallel City (BKT 145) was discarded