I don't see what else they should have done? This researcher made some ultimatum. As part of it, she said if Google refused, she would set a date to leave the company. Google obviously did not concede to her demand, and obviously didn't think it beneficial to let her be a thorn any longer, so took her up on her offer.
Seriously, I'm kinda a little wondering how people expect that when someone makes an extremely demanding ultimatum that includes challenging the rights of other people in the company, and the company declines to agree to that ultimatum, that we should be shocked that the person doesn't get to dictate all of the details around their resignation.
What I get most from this whole discussion is the extremely nauseating level of entitlement from some employees at Google.
If I storm into my manager's office and demand a set of conditions, or else I resign on some date, and my manager says "Well, fine, we accept your resignation, but it's effective immediately" I don't really have a problem with my manager calling it a resignation.