Statements contain primary, secondary, tertiary, and quatnary meanings and nuances.

I don’t understand how anyone could...

There's a simple example of a case where the secondary meaning supersedes what I'm temporarily calling the primary meaning. The above statement is incorrect in a primary sense (in truth, they believe they understand perfectly well), and correct in a secondary sense of what they're really trying to convey. The user is operating in the secondary sense when they speak.

But here's the fun part - people usually don't know which sense they are operating in. They operate in all of them simultaneously. They bleed over, too - sometimes, if they say something in a secondary sense, they will fool themselves into believing the primary sense, and so on.

It seems like they're not operating on connection to reality, but here is usually at least some level at which a statement implies a belief about reality, but it's not always at the primary level.

For most examples of where someone makes a statement clearly at odds with (to you) obvious truth, it's generally also possible to figure out a certain prediction they have about reality - it's just often hidden under layers of meaning and not explicitly made.

...on the surface appear to be about the nature of reality, but which really are about something else, where the precise value of 'something else' is unknown to me."

Right, exactly. Except that "something else" is also part of reality. So you are discussing reality, still, it's just conflated. Something is being lost in translation.

The thing is, not everyone conflates the same way, and some conflate more than others, so we are often bad at figuring out what is really being discussed, and that's where part of the divide and misunderstandings comes from.