When is it ‘wrong’ to put tabindex=0 on non-interactive content?

I'm trying to fix up a site made with the adaptAuthoring tool after an accessibility audit. One of the audit items is a complaint about the very large number of tabs needed to navigate the document.

Adapt sells itself on (amongst other things) accessibility features and even WCAG compliance. I have my doubts. Maybe someone here can help me out.

I've noticed that almost all content generated by adapt authoring is given tabindex=0, even non-interactive content such as headings, lists and paragraphs. This does not seem like 'best practice' to me. It certainly requires dozens of additional tab-strokes to navigate documents made with the framework.

I've seen it mentioned in many places (especially including w3c documentation) that all interactive content should be available via tabbing, and that tabindex=0 provides that functionality in those cases where the element is not focusable by default.

From that we might conclude that non-interactive content should not have the tabindex=0 setting, although I have seen examples where (e.g.) ordinary paragraphs are given this setting.

As I understand it 'virtual mode'/'browse mode' should be sufficient for reading text, and it's clear that the extra tabstrokes get pretty tiresome when browsing non-interactive content, not least because screenreaders often announce the type of the elements as well as the content, but I haven't found an explicit recommendation not to use tabindex=0 in these cases.

So, did adapt do the wrong thing? If so, I want to file a bug with them.