Yes, it is. Although https://www.gnu.org/licenses/agpl-3.0.html says

> All rights granted under this License are granted for the term of copyright on the Program, and are irrevocable provided the stated conditions are met.

it also says

> You may not propagate or modify a covered work except as expressly provided under this License. Any attempt otherwise to propagate or modify it is void, and will automatically terminate your rights under this License (including any patent licenses granted under the third paragraph of section 11).

> However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

> Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

This is in common with the GPLv3. It is much longer than the corresponding terms of the GPLv2 to remedy a sort of fragility in the GPLv2 which says your license terminates permanently if you ever violate the GPL, even temporarily and by accident.

I have no knowledge of whether Weka did or didn't violate the license, but if they did violate it and refused to fix it, MinIO's revocation of their license is completely in accordance with the terms of the license as written. I don't think a GPL termination case has yet been litigated.