I suspect from the tone of the email that the manager may have already tried that route and gotten pushback. It feels very much like a manager who is tired of the excuses and trying to be as unequivocal as possible so as to be 100% clear.
And that's assuming we even have an accurate statement, which is a big assumption. Aside from the missing context, we frankly don't know that any of this text was written by the manager.
Depending on internal policy, this could be reason enough for the employee to be fired.
Unless explicitly authorised, I’m not allowed to quote an internal email on a public forum.
As I read it, it looks like it was decided, by IBM, the employee would no longer be a maintainer and adding a personal email to the list of maintainers was a misrepresentation of their current role.
I suspect that HR is probably discussing termination procedure as we speak and this will proceed unless the PR pressure is overwhelming and makes it difficult to retaliate.
And that's assuming we even have an accurate statement, which is a big assumption. Aside from the missing context, we frankly don't know that any of this text was written by the manager.