Although there is nothing wrong in tiling over bonding, providing is dry and sound, I'd recommend skimming before, not necessarily smooth as it's going to be covered with adhesive anyway.
Bonding is kind of porous material and takes away moisture from adhesive too quick, this accelerating adhesive setting hard and not allowing chemicals doing them reaction. Never tile over fresh bonding, the tiles with adhesive and bonding might fall down altogether. I'd recommend not grouting tiled area the same day, except for using rapid set adhesive. Applying a thin skin of multifinish will seal the bonded area and create adequate base for tiling.
Hope this helps.
We do a lot of bonding for tilers and never any problems, British gypsum do say that you shouldn't tile onto a backing plaster but I suspect this is so they can sell more plaster.
Get it plastered ltd
If your walls are reasonably flat then their is no need to apply a skim finish you can tile straight onto the bonded wall.
Please ensure there is no dust and the surface is flat
Thanks for your enquiry