Ceramic Tile over Peel and Stick?

My wife and I hired a tile installer to lay ceramic tile flooring throughout a portion of our home. We had the same tile installed in the back half of our house a few years ago and love it, and so we decided to hire the same guy to do the remaining living space while we were out of town, as he did a great job at a reasonable price.

Fast forward 3 weeks, and to our complete frustration, the job still is not done. However, because he did not complete the install before we got home, I was able to see that he did not remove the cheap peel and stick laminate flooring that the previous owner had installed, and is laying the ceramic tile right over top of the peel and stick.

He has assured me that this is not an issue, as "gravity will do what gravity does" and everything will stay in place, however, my limited googling is telling me otherwise. So my question for you all is, will laying the ceramic tiles on top of the laminate peel and stick become problematic down the road?

Some relevant info:

The subfloor under the laminate is the finished concrete slab foundation, so no movement issues there.

The peel and stick laminate is the cheapest of the cheap. It is super thin, with no padding or cushioning on the bottom. It has no give when walked on or placing furniture on.

This guy assured us the job would be finished in the 3 weeks we left town, but it is maybe 75% completed, and he is only working 3-4 hours per day, so I am starting to question his integrity/trustworthiness.

Flooring sub, please talk me off the ledge here!