The downside of having an adorable magizoologist as a boyfriend is that sometimes he has a magical creature that likes shiny things, which makes it very difficult because Graves is trying to propose with a shiny thing.

Graves is trying to propose to Newt but on the big day he couldn't find the ring in his pocket. He knew the NIffler must've took it and gave chase but Newt was faster. Newt found the ring and when he cast a spell to find its owner it lead back to Graves, so Graves just threw away the romantic proposal plan he had and just proposed then and there.

Totally fine with fluff and schmoop, in fact it's very welcome.