I can’t speak for the Hamilton developers, but I don’t think that was their goal. And it is not our goal to dictate to developers how their apps should look and act.

Try the Flutter Gallery app. In it, the user can open the menu drawer with a swipe. Note the menu items that let you change the app from Android to iOS look and feel (including differences in scrolling behavior). There are other changes you can play with.

If you are really concerned about having pure material design widgets, you should play around with some of the sample apps included with the Flutter installation. I think you will really like the Flutter material design widgets.