[…] a phenomenon known as vergence-accommodation conflict (VAC).

That’s because the brain is fooled into thinking that a virtual object is some distance away, when the reality, of course, is that the displays are very close to your eyes.

This is a very common misunderstanding, but "the displays are close to your eyes therefore you get VAC" is just wrong.

Yes, the display is close to your eyes, but there are lenses that move the focus plane further away. VAC comes from the fact that that focus is fixed, and looking at something close by would mean you’d still have to focus your eyes further away to see it sharply. There are (research) headsets with the displays just as close, but with something in them that let you focus on different planes (e.g. movable lenses).