Exactly this! " the house is completely in control of what tiles the mines end up on for every game." I will give you an example of what is happening there: If you play like 100-200 games with low money at certain squares, you will notice that bombs will start appearing more times at that specific squares. You could exploit a house by doing that.
But still this is based on your theory right? If this can be proved so everyone will be profitable to play on their site, on which gambling industry never give easy money for players here. And btw what is max bet and max profit there? I do not think that they really have a big whale to play there since their is not a provably fair like RGB said before