Not if you're trying to make a playful app design like the author is doing. This design is halfway between a normal application and a game.

I would do silly things like clickable image views to get the style right if buttons don't provide the necessary customisability, were I in the author's position. I don't think anyone would be happy with that.

I'm all for platform consistency, which there is very little of these days, but for every API you restrict someone will find a good reason to work around it and that's where the ugly hacks come in.

Really disagree with this. Apps are rarely unique to a platform, and most users aren't on a single platform. I want Google Maps to look the same on the web regardless if I'm on macOS, Linux or Windows, and on my Android phone.

On the web that is fine. As a native app, it should fit in with the platform. On iPhone Google use the Android design language, and it produces apps which simply do not meet expectations.