I don't think it's crazy that you don't get evergreen upgrades to a system you've already bought, especially when you can just upgrade the motherboard to the 12th gen (which is actually the core value proposition of framework) https://frame.work/marketplace/mainboards
They do address it in the post:
> For 11th Gen systems, we also have a firmware update in progress to bring in the security updates and power consumption improvements, but not retroactively certify Thunderbolt (there are some test cases we don’t believe we can resolve on that generation, unfortunately).
Sounds like a hardware thing, which again you can upgrade