No thinset under cement board

[Michael Herr]

Just went to inspect some work and noticed they weren't using thinset to lay down the cement board under porcelain tile.

When I asked the contractor, he asked his flooring guy who had been doing tile for 25 years and "never puts thinset under cement board".

Our agreement was to put down cement board and tile.

Nothing was specifically said about thinset. The manufacturer dictates to use thinset between subfloor and cement board.

It is 1/2" durock over 1" nominal thick plank.

For the record, this is my first time really contracting anything. It's been all me and cheap DIY/Craigslist hacks before this, so I am willing to take pointers on how I could have/should have done something different.

Should I have been more specific in work instructions?

Should I demand he redo the job to what I think is the right way?

Should I meet him in the middle and pay a bit more?

Most of the 375sq ft of tile is already down.

What would you do?