This note in https://drafts.csswg.org/css-display-4/#order-accessibility

Authors must use order only for spatial, not logical, reordering of content. Style sheets that use order to perform logical reordering are non-conforming.

NOTE: This is so that non-visual media and non-CSS UAs, which typically present content linearly, can rely on a logical source order, while order is used to tailor the layout order. (Since visual perception is two-dimensional and non-linear, the desired layout order is not always logical.)

Makes two assumptions:

• non-visual ~= linear
• visual ~= multi-dimensional non-linear

IMO, neither is correct, even though it includes the work "typically"...

"typically linear" might only be true in the case of a novice, sighted screen reader user like a web developer.

Suggestion:
NOTE: This is so that non-visual media assistive technologies and non-CSS UAs , which typically present content linearly, can rely on a logical source order, while order is used to tailor the layout order. (Since visual perception is two-dimensional and non-linear, the desired layout order is not always logical.)