there is a work around, i do not know if it is posible to adapt to B4A
you must use gesturedetector.
set the gesture detector to the inner scroll view and use the reflection library like this (on the event of touch of the inner scroll)
Dim r As Reflector
r.Target = parentscrollview
r.RunMethod2("requestDisallowInterceptTouchEvent", True, "java.lang.boolean")
i use it once for a draggable view within a scrollview and worked so i do not really now if it will work for 2 scrollviews.