Former software revisions cannot predict all functionality we add. So we can support upward compatibility but not downward compatibility under all circumstances. Exporting/importing Performances via USB-memory stick doesn't resolve that. But not knowing the concrete OS revisions involved, I'm not even sure there is any relevant compatibility restriction.
Why can't you export your Performances via your Rig Manager, store these on your USB memory stick, and import these from this USB stick via their Rig Manager onto their PROFILER? By doing so, you can avoid accidentally overwriting one of their production Performances with one of yours. Since every Performance has a fixed location and the number is limited to 125 import needs to be a managed process and that is possible via Rig Manager.
In this case - they don't have a PC with Rig Manager to support them. Most guitarists come in and use what's on there - in my case, I just wanted to use my performance on their Kemper as opposed to hauling in my own gear.
If I want to see this through - I'll probably uninstall rig manager on one of my own laptops, install an older version of rig manager on said laptop, and then use it to try and connect to their OS, which is on OS 5.x. This is doable, but I'm not wholly understanding the response from you - I haven't seen a technical reason for why the Kemper can't allow me to import from USB and prompt me on which slot to import the performance into. Add on that, doing away with backwards compatibility on Rig Manager - and again, it's frustrating.
I'll be honest here - in and of itself, this would be a mild frustration and not a big deal. But when put into context with the Stage's release where we had to endure a multitude of releases before we got something that was stable (while being told the programmers were on vacation, so we should 'enjoy summer, be happy and play our guitars' right after dropping $1,700), it's becoming part of my broader frustrations with the Kemper system.
Between using a Toaster since 2016, and being an early adopter of the Stage, I've been pretty invested in Kemper, but if this is going to be the response going forward from Kemper.. then that's disappointing, to say the least.