Just going to throw this out here... it sounds like the s/w isn't actually created for the Ranger - which is probably why it isn't sold with it. I realize there are some things you can do in Forscan to change how things work, but then there are other things that you can change in Forscan, but doesn't actually change how the truck works.
The main example that comes to mind on our 5Gs (which run Sync3, not Sync4 - though perhaps you have a MY24+ 6G, which does come with Sync4) is that you can enable the climate screen on the RHS of the Lariat cluster. But you can't actually control anything from it, and it freezes up if you do.
This iACC sounds like the same thing. It has some code there, perhaps at one point it was going to be a feature, but then it was canceled or abandoned or whatever reason pulled from the program, so the code remaining is incomplete because it was never followed through.
Well, it's a bit more complicated than that. The software is written to read settings from modules and write back where supported, when using the required hardware interface. The IDS software/hardware kit the dealer uses wasn't written for the Ranger either. If you can decipher all of the module configuration lines you can change them in that module, but if you forget to update a supporting module to receive/reply it could cause the first module to hang and get confused by the other ignoring it. With the climate example, I would think enabling the on screen controls is part of the process, the climate control module may need to know that it should listen to commands from the sync system and maybe even what version sync it's replying to in order to understand the incoming command and format the reply in a way that is understandable to the sync module.
Also, there can be hardware differences between trims or regions that even if you try to enable a feature, it simply will not work. On the Focus RS we found that if we installed the EU light controller and set the BCM to support the rear fog light, when we pressed the button, the dash would properly indicate the rear fog light, but the 12V output from the BCM never enabled, so some internal circuit is not present in that hardware as far as we can tool (or the programming logic has a region check in addition to the rear fog light setting that results in that path to enable the light never running).The best option we've come up to use the EU light switch to control the rear fog with a Pi on the network monitoring for the message between the light switch cluster that controls a relay for the rear fog, or someone mentioned tearing into the cluster and tapping into the rear fog indicator light to control the relay.