I think we knew this already, but perhaps this is just a more detailed confirmation.

I'm not surprised that Reeves was interested in exploring other origin stories, we had an already captured Joker in the film itself (or just a deleted scene?) and we got the spin-off of The Penguin to give that character more story.

I expect a Clayface film set in the Matt Reeves universe would be less melty. I think we'd probably get some face or maybe voice changing, but I don't think it would be as gruesome.

Although if the comparison is to The Fly and without knowing how "fantastical" Batman II will be... Maybe the universe would have shifted a bit and allowed for it.