I'm not doubting what happened in your wife's situation, but it strikes me as strange that this would happen at a company where both men and women are given longer parental / bonding leave than is required by US law (and, in China, more than is required by Chinese law). The obvious reason why the company would offer this, is because it helps with employee recruitment, retention and productivity over the long term.
And, given how hard it is for large companies in the bay area to hire enough people who fit their needs, it seems irrational to let someone go for only this reason.
That helps the company in general, but on individual teams the incentives are different and the manager may have decided it was worth it for him to try and kill this behavior or just get the employee gone now so that he could get in queue for getting a replacement ASAP.
And, given how hard it is for large companies in the bay area to hire enough people who fit their needs, it seems irrational to let someone go for only this reason.