Does Turtwig's evolutions count towards Celebi's research quest?

Niantic responded to my inquiry, and this is by design. Generation 4 evolutions will not work for Celebi's Special Research.

You need to evolve an already evolved Grass-Type Pokémon from the Kanto, Johto or Hoenn region. Please excuse the circumstances that have been caused. Unfortunately, Pokémon from the Sinnoh region do not work.
_{(Response from Niantic support)}

Apparently, users on reddit (here and here) are reporting that evolving Grotle into Toterra does not count towards Celebi's research quest.

There have been known issues in the past with Celebi's field research. Given that Grotle is Gen4 and was released after Celebi's field research, the consensus between the two threads is that this is likely due to a bug.

I reached out to Niantic in regards to this, and will update my answer when I hear back.