Clarification on ABV-tagged entities in IFC4x3 Add2 Annex B

While reviewing the IFC4x3 Add2 documentation (Annex B – Alphabetical listing of entities) https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/annex-b1.html, I noticed that only some entities have the ABV tag.

Questions:

1. Does this mean that only entities marked with ABV are officially part of the Alignment Based View (ABV)?
2. Are entities without the ABV tag excluded from ABV exchanges, or can they appear as supporting elements?
3. Also more details/example links related to ABV implementation would be helpful