Re: Could it be that security fix requires hardware that is younger than three years old
A security fix almost certainly doesn't make the OS require any better hardware than it did before the fix was applied.
If the OS vendor chooses to issue fixes by rolling them into updates that increase functionality, and so may require a different standard of hardware support that would be a different matter ...
... and we would be entitled to shout DON'T DO THAT! (... not that the vendor would take any notice.)