For Bruno to successfully play at false 9 the rest of the team would have to be much different.
The reality is, one of the reasons Amorim keeps bouncing him about is because he needs someone with Bruno's energy and workrate in midfield who can also progress play. We have runners in midfield, Ugarte and Collyer would rat about til the cow's come home, but they're not exactly incisive passers. So Bruno gets stuck playing #8. Even though that basically kills any creation from #10.
When we're desperate Bruno gets sent forward, because he's the most dangerous attacking threat we have. But we don't consistently progress the ball so a lot of the time its just him standing around waiting for passes in the channel. Playing him as a false #9, in this set up, would probably just make it worse and we would lose his legs on defensive transitions.