After moving from Godot 3.2 to 3.4 I wanted to set up android export and saw a requirement for NDK in Godot docs. But I skipped it and my android exports seem to work fine. So I'm wondering where the NDK would be needed and how it'll come into play later.
I think it is needed for compiling a custom module and/or build of Godot for Android. If you are just using the export templates from a Godot release, then you may not need the NDK at all.