Has to do with the boards I believe. Stern uses proprietary boards (spike 2) that are more than likely hard coded for the version to run the things that aren’t on the pro. JJP has dongles on the PC that are matched to the version of their games, hence why they have a single download for all versions. If you put pro software on a stern DP for instance, the drop targets don’t function correctly because the pro doesn’t have them.