As someone who's worked in (US) Healthcare IT for over a decade, I suspect that many of the lagging devices are running a LTSB/LTSC build of Windows, which receive updates for 5-10 years rather than the 2-3 years for standard releases.
https://learn.microsoft.com/en-us/lifecycle/products/windows-10-iot-enterprise-ltsc-2021
https://learn.microsoft.com/en-us/lifecycle/products/windows-10-iot-enterprise-ltsc-2019