They don't have to. It could just give a warning with something along the lines "Your current hardware setup is not supported by Windows® 11. By continuing you acknowledge that you're proceeding with the upgrade at your own risk with no guarantees from Microsoft® and that you won't be entitled to any support from Microsoft. The risks include but are not limited to: OS failing to boot-up; frequent BSOD; programs unable to install; certain parts of Windows® operating system not working; data loss; non-functioning or only partially functioning hardware; violation of applicable laws; permanent hardware damage; or causing damages to property and/or bodily injury, including death as a result of improperly functioning drivers. While we understand this may seem harsh, we do not know how the hardware will perform under these conditions and therefore we want you to understand the potential dangers and that you are responsible for any repercussions. We strongly recommend upgrading your hardware to meet minimum requirements for running Windows 11."

"Do you wish to continue with the upgrade?"