Of course they would discourage them from deviating from Realpage's recommendation. Why are you paying for a software that recommends the most profitable rent if you aren't going to follow it? Realpage doesn't want property managers to complain that the software isn't working when they're ignoring the software's recommendations.
I have yet to see any evidence that there are any actual consequences of ignoring the recommendations. I'm assuming that Realpage will always accept payment for their services. This suggests that price fixing is unlikely. In the case of a cartel, members are incentivized to sell more than their quota allows, and you need active enforcement to maintain compliance. See the history of OPEC.