Yup, dev is aware of the problem, he has plans to optimize and fix few things here and there for android build.
Thing is, Android isn't the main focus when it comes to relase platforms, rather it's PC, the code is written to be launched on PC and Godot engine just gives the option to export the game as Android executable - this is exactly what he did. As I mentioned above, he has plans to rewrite some parts of the code so that the game runs better on both Android and Windows, not sure when tho.