I have done this a few times myself but used Thistle Bond-it to prime the boards with first.
This is ****** up this. No wonder ure calling yourself cowboy
the architect is a knob, hardibacker 12mm boards are for wet areas only like around shower/bath areas. Its a tile backing board for tiling and tiling only.. its got similar properties to the moisture resistant PB which is also not primed and designed for tiling.