Planting pockets in new patio
My new 'yarden' is almost complete, but I'm worried about the planting pockets. The landscapers laid dark grey hard-core over the whole yard after breaking up and removing the old concrete surface. They then laid a yellow gravel/sand-like material where the patio stone would go. Then once the stone was down, they infilled the planting pockets with topsoil, without removing the grey hardcore in these areas. Was this correct? I have a sign off meeting with them tomorrow and I'm concerned they'll just say it's fine, as to remove and dig up the grey hardcore would be additional time and effort for them. The part of the job they haven't completed yet is to provide a planting plan, so they are combining the sign off meeting with a visit by their gardener to discuss this. If both people visiting say its OK the way it is I haven't got the expertise to disagree. I've mentioned it twice in emails to the company, once my question wasn't answered, and most recently they've said they'll consult the gardener on it, but haven't got back to me.
I want at least one tree in the garden, as well as climbers all around the walls, so I assume I need to dig a fairly deep hole, at least for the tree.
Can anyone advise if a layer of hardcore between topsoil and the natural soil (which I haven't seen) is ever correct? I'd like to be armed with some knowledge tomorrow.
And I don't want to spend money on plants that won't thrive. I'm deliberately having beds rather than a container garden to allow my 'yarden' to be more self sufficient for watering etc.
Pics below show the grey hardcore, the yellow surface and the finished surface.