This may be a bug, which should be reported on GitHub - godotengine/godot: Godot Engine – Multi-platform 2D and 3D game engine with full device information and a reproduction project included. The Godot 4.x Compatibility rendering method hasn’t been around for quite as long as Godot 3.x’s GLES2 renderer, so it’s expected to have more bugs.
PS: Remember that if you create a project and switch its rendering method afterwards using the dropdown in the top-right corner of the editor, its mobile override won’t change automatically. You have to change it manually in the Project Settings.