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it was tested recently on variable power moves including Hidden power and it does boost them has long has they are 60 BP or less if they are over 60 BP then it doesn't boost
Both persian and ambippom learn nasty plot. Persian can hypno plot and use thunder bolt/hp ice. while ambipom can nastyplot swift, water pulse, shock wave, thunderbolt, and hp ice. And after a nastyplot they can deal some damage.
No, they are not causing any damage at all. Walled by Blissey/Snorlax/Regice/etc. anyone? Ambipom solely aims to pass those boosts, and Persian is only usable in the lower tiers, which isn't even that great because the most common special wall is immune to sleep.
technician hidden power is pretty much only usable on persian as ambipom is always gonna pass the nasty plots onto something else and its filler attack is usually thunderbolt for skarms that come in and try to whirlwind it.
Obviously on persian, hidden power is used in the hypnoplot set. HP fighting 60 is also a viable option on its physical sets to hit the rock/steel pokemon like aggron 4x effective.