Your Office of Technology isn't giving good advice on this.
Container tags ( <Part> <Sect> <Art> ) do not affect most of today's assistive technologies (AT). Most, at this time, ignore them. See details about PDF/UA tags at https://www.pubcom.com/blog/2020_05-02_tags/pdf-ua-tags.shtml
So whether the document is short or long, they're not affecting the end users' experience. They could, however, provide some valuable information to end users...if assistive technologies would use them, but none of us control what AT does to a file.
However, we have begun to see container tags affect certain AT that reflow the content — especially non-PDF/UA compliant AT — and we expect to see more of that in the coming years. So they should be helpful for any length of PDF, not just long ones. Q: how do you determine what's a short or long document? How many pages? Those terms are subjective, not definitive.
There are situations where container tags cause problems for those who review and test PDFs, like maybe your office of technology. They do slow down a sighted reviewer and force them to expand/collapse the tags to examine the interior tags. But again, rarely is the end user affected one way or another with container tags.
At the end of the day, we're required to comply with the recommendations made by our OIT team so I don't think that this conversation is helpful or answers my question.
We prefer not to use container tags and I'm looking for an easy way to remove them. It appears that's not possible in Adobe without CommonLook.