It's the behavior for all apps and I don't think it can be customized. There are some APIs to affect the spot shadow color and ambient shadow color (from API 28), but no way to affect this offset / light source position AFAIK.
Yeah, that's normal practice and usually works OK. But then sometimes it happens that the given elevation value give a shadow much weaker than in the design tool.
Especially for things like a bottom toolbar where the top of the shadow is close to the bottom of the screen and supposed to visually separate the toolbar from content. Another toolbar using the same elevation in another place on the screen may look fine.
So when QA say that the shadow is too weak, you have to tell your designer this and they have to come up with something different, or you have to increase elevation to compensate, or fall back to a pre-rendered 9-patch, or something else... As i said, annoying :\
Another really annoying fact about drop shadows, is that Android choose to implement the light source pretty much where your nose is. So when a view with drop shadow moves closer to the bottom of the screen, its drop shadow increase visibility at the bottom of the view and decrease visibility at the top. This makes it's impossible to match specs given by designers on Android.
