They're not flipping a kill switch on these devices. They just won't be running the newest OS. I don't see how these two things (software updates and hardware longevity/recyclability) are at all related.
The main issue is, as the article points out towards the end, that you only receive all macOS security updates if you are on the latest major version. The two major versions prior to that one receive some, but not all, security updates. Once you are three major versions behind, your Mac does not receive any macOS security fixes anymore, which of course is hugely problematic.
So yes, unless you are completely ignoring the security of your system, losing macOS support is a kind of soft kill switch for the hardware.
There's another way which you could see this, which is that the cost of maintaining backward compatibility for every prior piece of hardware only increases the surface area for vulnerabilities to emerge.
Also, if security is your #1 priority you should pay the cost of the upgrade. Monterey is compatible with Macs as old as 2015. That means that Apple will sunset security support for it in 2024. That's nine years of supported life for your computer – not bad.
The problem I've run into is other software/libraries dropping support for older versions of MacOS. So far this is fixable, but it means if you need new features, libraries, or whatever in other, non-Apple products, you might not be able to get it. In these cases, there's nothing functional about the decision, it's just "we're cutting off support here". That is, I could install Linux on my Mac, and run the latest version just fine.
This isn't Apples fault, but the whole thing is sort of ridiculous to me. It puts real pressure on me to upgrade hardware for it's purposes solely because of arbitrary software support cutoff decisions. It would be different if it were "version x needs this hardware feature" but that's not the case.
Not releasing the source leaves you open for vulnerabilities and locks out independent development. So people dump these in favor of new ones but for doing the same thing
As a counterpoint, I have a 2011 MBA that I still use from time to time. It doesn't have half a decade of updates but it does everything that it used to do, just fine. I primarily use it as my no-distraction writing device.
So yes, unless you are completely ignoring the security of your system, losing macOS support is a kind of soft kill switch for the hardware.