This is not true, because if have some process internally on IDE to split the B4a and B4i portions of each platform, on B4xlib can have some common interface making this 2 libraries internally, in one cross-platform library.
Not just using the "same" B4x code, but using two different platforms and libraries in one common library.
This is exactly Xamarin Forms Cross Libraries do! Share the same layer, but inside have libraries for two different platforms.
Is like when you using B4i, you can see just the library created (.a, .h, .xml) and if you using B4A, the IDE can see just .jar and .xml