The initial RealFlight 8 release was published by Hobbico. Obviously some big things changed in the industry after that, and the RealFlight 8 Horizon Hobby Edition came out a year later. As the first RealFlight product released in association with Horizon Hobby, it was the first opportunity to include some of their very popular product lines in our sim. RF8 HHE replaced the previous RF8 release in stores, but if you purchased RF8 before then, the HHE Add-On was required to get those extra new models.
Note that while there may have been a delay in availability outside the US, the separate editions had nothing to do with region.
For RealFlight 9, our first new major version with Horizon, there is simply no need for a separate edition to more tightly integrate RealFlight and Horizon products. We have been working closely together from the very beginning. As you've no doubt seen, RF9 is full of Horizon models! And I think you'll be happy to know that it also includes all of the RF8 HHE models you're looking for.