To the extent that there systemic anti-maternity bias within Google, it is certainly below the background rate of society as a whole. That's not a very high bar to clear, so I'll go further to say that Google is actively supportive of parenting and maternity in a way that few other organizations in the United States are. I can say that as someone whose spouse has had two kids there, and as someone whose teammates have had dozens of kids between them during our time working together.
Even with that, failures like these occur, because that's just what people are like, and we have not designed perfect systems to counter this type of behavior. That's not to excuse -- if the story is accurate, figurative heads should roll. And our systems should be improved.
But positing a systematic policy of abuse like this is cynical and doesn't fit with the evidence. Doing so is less like extrapolating a line from a single data point and more like drawing an entire picture from that point.
But it may very well be that they are willfully (or simply incompetently) turning a blind eye in this one particular case.