>>26792224You could still have Softboiled Clefable in Gen 4-5.
If a Gen 3 Pokémon had their second ability flag when they didn't have a second ability, if they were transported into Gen4-5, they would get the second ability upon evolving.
This was fixed in Gen VI, but as you said it had the Ability Capsule so it was a moot point.
Clefable's OU came exclusively from its type change, +10 BST in Sp.A and Moonblast being bretty gud.