Pynq 2.5 overlay / vivado heirarchy query?

Should Pynq be able to recognise memory mapped components embedded at lower level in a heirarchy? or should all memory addressable componment be placed at the top level only.

I buried a module to tidyup my top sheet, and the Pynq overlay couldnt see it. Maybe ive done something wrong.

Using Vivado2019.1; Board ZCU102