Parsoid is going to start adding section wrappers in its HTML.

The details are documented in https://www.mediawiki.org/wiki/Parsing/Notes/Section_Wrapping.
T176959#3711269 is the current proposal that is awaiting a response from Reading, but once that is finalized https://gerrit.wikimedia.org/r/#/c/364933/ will be updated.

VE needs to be able to process Parsoid's output. The current plan is for VE to strip the section tags before processing the DOM. https://gerrit.wikimedia.org/r/#/c/364933/27/lib/utils/DOMUtils.js (line 2877) has some code if it is helpful. Parsoid accepts HTML with/without section wrapping. So VE doesn't need to add section tags after edits.