I’m sure that’s very frustrating. 
It’s not a GE/Jasco issue. Their devices are certified to the independent third party zwave standard and work fine with most certified zwave hubs.
From the beginning, SmartThings has added its own unique architecture over the top of that, first device type handlers (DTHs), then Edge Drivers.
Many manufacturers, not unreasonably, feel that since they have already invested time and money into getting certified, if a platform has additional unique requirements, it should be up to that company to meet those.
Unfortunately, SmartThings doesn’t see it that way. So there are sometimes feature gaps. The community often steps in and provides code that exposes more features. It is what it is. 
To find community-created edge drivers, check the quick browse lists in the community-created wiki. In this case, check the list for pocket sockets/smartplugs.
https://thingsthataresmart.wiki/index.php?title=Quick_Browse_Lists_for_Edge_Drivers
@philh30 does have a custom edge driver for GE devices that does include that model, but I don’t know if it gives independent control of the two sockets. You can ask in his author thread (which is the link you will find on the quick browse list) if you want to know before you try it. If you want to jump straight to his thread, here’s that link:
[ST Edge] Driver for GE/Jasco/Honeywell Z-Wave Switches, Dimmers, Fans, Outlets, and Plug-Ins
For the future, sometimes the smaller companies are more willing to put in the extra effort to keep up with SmartThings’ idiosyncrasies. Historically, as you noted, the Zooz brand from TheSmartestHouse has done a good job of this. However, there’s no guarantee that they or any company will continue to do so in the future—SmartThings has added extra cost and complexity to the integration process, and most companies are looking to go in the opposite direction. FWIW.