That being said, this story doesn't make sense unless it takes place outside of CA. Work for a PhD thesis is generally done on university grounds, giving the university the putative right to the underlying IP. A third-party employer like Oracle would have to duke it out with the university to claim ownership, no matter what their employment contracts said.
OTOH, if work for the PhD was done using Oracle facilities and equipment, then it makes perfect sense for Oracle to investigate IP ownership since many PhD thesis projects go on to become valuable commercial products.
It was without doubt a time wasting and frustrating shitfight ensuring he was "allowed" to think about his PhD topic after being acquired by Oracle (although he had enough equity to have done quite nicely out of the deal anyway, I suspect...)
> No, that would be illegal in pretty much every state, except possibly the worker-hostile US Deep South.
A friend of mine had to put his PhD on-hold when the company he worked for was acquired by Oracle, while his lawyer and their lawyers argued over whether the "standard employment contract" he was being asked to sign prevented him from publishing his thesis as required by the university to complete his PhD... A face value reading pretty much claimed "everything you think while employed by Oracle becomes IP exclusively owned by Oracle", and his new manager, their manager, and several levels up the corporate hierarchy all stuck to that interpretation for months before granting what was desc ribed to them as an "extremely unusual one-time-only expemtion which you musty not disclose to any colleagues".