Self-damage weakness metarule

[Magic_Umbreon]

Zapdos MD, Beldum DX, Wobbuffet PK and Mr. Mime MT have attacks that do damage to themselves, as well as a weakness to their own type. Each card has text to stop weakness and resistance being applied to that damage. Is that just a reminder clause like on pokémon that damage the bench or necessary to prevent the weakness being applied to self damage? Such as a Dratini DS with a crystal shard attached damaging itself without the clause or general confusion damage from Zapdos or Mr. Mime?

 

[PokePop]

There is no confusion damage.
Failing a confusion flip places three damage counters.
No Weakness is involved.

There is no metarule for this