Apple’s current 7 year cutoff includes radical evolutions of hardware over recent years.
The latest cutoff, as far as I know, is Macs that typically were sold with a spinning rust HDD - which are honestly useable anyway on the new filesystem which has been designed from the ground up for SSDs. Modern MacOS just can’t cope with seek time lag to access the disk.
The big cutoff before that was transitioning from 32 bit to 64 bit CPUs. And the next cutoff will be from x86 to ARM.
Apple doesn’t have a hard cutoff - they have a “we will support as far back as we can” cutoff, which is a combination of the cost required to keep it compatible and the number of actual users on old hardware.
Also - even after things are no-longer “supported” they often still get security patches from Apple. Especially if something is actually being exploited.