There is also an issue of hostile-ish fork. If you release something as (A)GPLv3-or-later, anyone can take it, and extend/change it. However, those changes can

There is also an issue of hostile-ish fork. If you release something as (A)GPLv3-or-later, anyone can take it, and extend/change it. However, those changes can be done under (A)GPLv3-only. That would prevent you from incorporating them into your version (unless you also re-license to (A)GPLv3-only), while they still could merge anything you add. In general (A)GPLs care about user freedom, not a developer freedom. So this is not seen as a flaw. I personally prefer using -only variants, since it seems to strike reasonable balance in this regard.