I wouldn't consider the Pentastar to be a low compression engine with it's 10.2-1 ratio. Most engines that have knock sensors will benefit from higher octane gas.
It may take a couple of tanks for the computer to slowly raise the timing from the lack of knock detected. I would think the programming would be based on averages over a period of time when determining timing to run. Kinda like the fuel trims do. GM's do this, not sure of Chrysler programming.
The ECM will try to run as much timing it can, up to the limit programmed. I doubt any engine running 87 will be at the upper limit. You'll need to log knock retard, with a scanner, to see how much timing is being pulled for each fuel. More timing means more power and better fuel economy.