[CodeWriter23]

I think this all turns on, did the original author assert "Addtional Terms" under GPL v3 7e:

e) Declining to grant rights under trademark law for use of some trade names, trademarks, or service marks; or

If he did not, it would appear to this non-lawyer that he released the icon and branding under the GPL.

[kube-system]

The author does not have to assert those additional terms to have trademark protection, because the law provides for that by default, and the GPL v3 does not have a trademark grant clause.

GPL v3 e7 means that, if for whatever reason, you do explicitly disclaim trademark grants, it does not violate or invalidate the copyright license.