I noticed that my iPad mini 2 finally falls off the list, but that thing is somewhat ancient.
However, my Thinkpad X220 (maybe circa 2011?) still runs Windows 10 and Ubuntu, allowing it to stay up to date on security patches. In a way, Apple's support levels are only impressive because we're inured to quick device expiration in other contexts (e.g. phones).
To be fair, mobile development is a few years behind laptop development, and it makes sense that it would plateau later (thought with the current generation of smartphones we may be reaching that plateau).
A 2011 MacBook Pro 13" is comparable to your X220 (dual core i7 available, 8GB supported RAM, Intel HD 3000 graphics) and while it does fall off the supported list for macOS Catalina (mid-2012 MBP is the earliest supported) there's no reason to expect it wouldn't run Windows or Ubuntu comparably to the X220.
When comparing (tablet) apples to (tablet) apples, I wonder if any of the tablets mentioned here are still supported in 2019 like your iPad mini 2 was? https://www.zdnet.com/pictures/best-android-tablets-septembe... It's a genuine question as I'm not that familiar with the Android ecosystem.
I think it's only a matter of sales strategy instead of a technical one.
They (be Google, Apple or whoever makes OS and/or phones) have the know-how and the tech to support older devices for a longer time. Even if they limit that support to only publish security updates for older systems (which, IMHO, I think it's the correct thing to do). Come on, see the Windows XP latest updates.
A phone it's not different. In it's core, It's a f computer running software. The main difference is that the average Joe is accustomed to replace them even quicker than desktop/laptops.
Apple et al are fixing the "errors" they made with the personal computer market: support them for a long period of time, or giving the devices a longer (and secure) life via security updates, so your sales plummet.
I think it's very unlikely that older Android tablets are supported by their manufacturers.
Of the 9 tablets and 8 phones in my sock drawer purchased since 2012, only the iPad Pro 10.5", Kindle Fire HDs, and Galaxy S8 are subject to continued upgrades. The rest are likely vulnerability Petri dishes that should never be allowed on the internet unless unlocked and moved to community builds (for the Android devices).
On Android if you are lucky, you would get one OS update and around one or two security updates. This on flagship devices.
Even Google's, are only guaranteed to get updates for three years, starting from the year the model was initially put on sale.
In any case, at least in most European consumer shops, you will see that the large majority of OEMs are migrating to hybrid laptops, convertibles with Windows 10 on them. The Android tablet section keeps getting smaller.
However, my Thinkpad X220 (maybe circa 2011?) still runs Windows 10 and Ubuntu, allowing it to stay up to date on security patches. In a way, Apple's support levels are only impressive because we're inured to quick device expiration in other contexts (e.g. phones).