It's not, and I already covered this.
AGPLv3 has nothing that is a direct superset of Apache 2.0's requirement 4b.
The closest is the section "5. Conveying Modified Source Versions." However, the terms are not the same. Section 5 is a subset of 4b, not a superset.
Specifically, 4b pertains to individual files, 5 pertains to the "work" as a whole.
The requirement to mark each modified file is not present in AGPLv3, ergo it's not a superset.
Also worth noting, in section 5 of the AGPLv3:
> Inclusion of a covered work in an aggregate does not cause this License to apply to the other parts of the aggregate.
The AGPLv3 is very explicit that it's on terms do not replace the terms of its aggregate components.
i.e. You can license a whole work as AGPLv3, but the components are still Apache 2.0. To use those components, you must adhere to those terms.
In this case, if you modify Apache 2.0 files, you must still indicate you've done so. So Minio should not be removing the Apache 2.0 from the repository, doing so is a violation of the Apache 2.0 and may cause contributors and users to also unknowingly violate the Apache 2.0.