Reflow does not follow the order of the logical structure as determined by the tag tree in the Tags Panel in a Tagged PDF, even though the docs say it does 1.

Instead, it follows the “page content order” (PDF 1.7 § 14.8.2.3), which is not accessible as it depends on the graphical structure of the PDF and has no connection to the tags in the PDF. Creating a PDF in which both orders are coherent is plenty of times impossible, and pretty much always impractical.

AFAIK, this makes Acrobat’s reflow feature non-compliant with WCAG 2.1/2.2 11.1.3.1 “Info and relationships” and 11.1.3.2 “Meaningful sequence”, which is the basis for EN 301 509 in those regards. The latter articulates the accessibility requirements for software in Europe as per the European Accessibility Act and is the base for similar regulations in other parts of the world.