The section tag and the article tag are "semantic" tags vs more generic tags with similar functionality like "div". They form the basis for epub semantics and in combination with epub:type and aria role attributes added to them allow the page to be more easily navigated by those with Accessibility issues using Screen and/or Accessibility readers.
Epub Accessibility in general has become increasingly important and especially for those in Europe with its recent law changes.
See for example:
https://www.accessiblepublishing.ca/...ic-aria-roles/
https://www.w3.org/TR/epub-ssv-11/
https://idpf.github.io/epub-guides/epub-aria-authoring/