Zombie Villager in a boat cured instantly

Tried to "catch" a zombie villager in a boat, had a heck of a time, so I left him in there to cure him rather than try and move him further. 

Threw the weakness potion, all good. 
Right-clicked with the apple - instant transformation. No shaking, no time-lapse, no five minutes- Instant. 

Then I had a villager half-in-half-out of a boat like similar listed bugs.