Just to reiterate: the observable consequences of that "hijacking" is apparently an almost imperceptible icon most people don't even see. That cannot be worth getting this worried about; the worry
needs to be something else, probably something that hasn't happened yet but the maintainers feel like it (whatever it is) is something terrible they believe the foundation now has the capability for, and do not entirely trust the foundation to refrain from exercising this unknown power in some future circumstance.
If that sounds absurdly vague, it's because the concrete accusations are that vague.
On the one hand: it's possible this tiny UI change does signify some deeper permissions change, but it's not exactly obvious what that would be (especially given the already admin nature of the dnfadmin account). Nor is it clear both the foundation and maintainer really understood what that permission might mean, if it even exists. It's not clear the maintainers have any specific reason to object in the first place!
The one thing that seems clear is that the github UI wasn't clear, allowing the maintainers and dnf to read very different things into a superficially trivial change, and that there's some level of miscommunication at the very least. But it's still not at all clear whether the actual change made warranted the fears expressed, not at all.
Personally, while the dnf clearly and objectively failed in its task of keeping maintainers on board, I can't help but also feel that these maintainers deserve a bit of opprobrium. They essentially started a major social media freak out, and cannot even express exactly what it is they're afraid of, let alone point to any evidence that whatever mistakes the foundation made weren't fixable by measures with less collateral damage.
It's all very nice to blame some scary sounding not-entirely-defined shadowy corporate conspiracy between github, microsoft and dnf, but at the end of the day meltdowns like this do harm, and it's just not clear that was at all warranted.