I think their point was that if you want fonts to be bigger, there are settings to do that. (or should be even if the world isn't perfect yet) Same to a lesser extent for other ui features.

In reality, as of today, so far, neither desktops nor apps are that good where you can have the display set at it's correct native resolution, while having buttons, menus, icons, text, window controls etc all scale to preference.

But saying that that's what should happen rather than lie to the software about the hardware, is not agist or ableist.

I think the point was simply that fundamentally, lying to the software about the hardware is always inherently doomed to produce some form of incorrect result, and when it does, it's not the tech's fault for failing to second-guess, work-around, and essentially thwart your actively dishonest misconfiguration.