The 50% heal only applies in Alola; before then they were terrible berries all around, healing only 12.5%. When they were upgraded to 50%, that level was generally considered to be overdoing it, allowing Gluttony users like Linoone or Snorlax to use Belly Drum and heal all the way back to full; Snorlax could also use Recycle as a makeshift version of Recover to get its berry back over and over again. As such, the Switch games rebalanced it by dropping them down to 33% healing, enough to be slightly better than the Sitrus's 25% but compensating by not kicking in until a more precarious HP threshold (so at best without having Gluttony, Cheek Pouch, Ripen, or Cud Chew, you'll end up at 58% instead of 75% with the previous behavior, or with Sitrus used at the edge of its range).
Of the five berries in this group (Figy, Wiki, Mago, Iapapa, Aguav), any given Pokemon is guaranteed to be able to use at least four of them without penalty; neutral natures (even if they later use a mint to change stats) can use all five without penalty. If a Pokemon consumes the penalty berry for its nature, the confusion is the only penalty; it doesn't heal any less than the other four berries would, but it doesn't heal more than them either. If there's an effect that blocks confusion, such as Own Tempo, then it's simply ignored just as if the Pokemon had a neutral nature and could therefore use all five berries penalty-free.
