Not A Bug Prankster Copycat Sunsteel Strike against a Wonder Guard Dark Type

[Tox in DbMaj]

What type of bug are you reporting? Mechanics

What is the bug?
Turn 6, https://replay.pokemonshowdown.com/gen7purehackmons-2223875556-afzolr5eb3ls666anczuycpn7gqiyxypw : Mega-Ray using prankster boosted copycat Sunsteel Strike didn't affect Muk-Alola due to Wonder Guard; or that's what the message says.
Rayquaza used Copycat!

Rayquaza used Sunsteel Strike!
[The opposing Muk's Wonder Guard]
It doesn't affect the opposing Muk...

I recreated this myself and the result was same.
Went ahead and tried to copycat ground type moves on Muk-Alola, in which case it triggers:

Rayquaza used Copycat!

Rayquaza used Mud Bomb!
(Since gen 7, Dark is immune to Prankster moves.)
It doesn't affect the opposing Muk...


So the question is, is it intended for dark types to be immune to non-status moves called through copycat? Even if so, I'd suggest changing the message for the Sunsteel Strike case to also be "(Since gen 7, Dark is immune to Prankster moves.)" as Wonder Guard wasn't protecting Muk-Alola from that move.

Are you able to replicate it? If so, how?
Put prankster ability on mega-rayquaza (any mon) with copycat and then bring a dark type mon with wonder guard (for sunsteel strike) and the ability doesn't matter for testing mud bomb or any other move.

 

[A Cake Wearing A Hat]

this would be because it's dark type, in actual function, yes. theoretically if this is erroneous it would simply be due to the ability splash itself; however, i do not know if the erroneous ability splash occurs on cartridge or not. If it does appear on cartridge, then this is intended behavior for PS and won't be changed.

 

[DaWoblefet]

Wonder Guard blocking a move happens prior to Prankster Dark-type immunity (see checks done before move success research). Moreover, when Sunsteel Strike, Moongeist Beam, or Photon Geyser are called by another move, they do not have Mold Breaker effects. So this is exactly what would happen on cartridge, and not a bug as a result.