I'm not at all surprised that Glassdoor is playing similar games.
The following isn't necessarily meant to disagree with you.
A common thread is that Yelp and Glassdoor directly make money based on their reviews. That's their core product. Other comments about how trust should be a core product are relevant, but that doesn't seem to be what's happening.
My wife and I started using Google reviews. To be clear: we are by no means starry-eyed Google fans. We're quite aware of many their problems and WTFisms.
In this case, though, unless I'm mistaken, Google reviews are at most very indirectly a product for them.
This is important, because in my mind, that makes it far less likely for them to meaningfully/substantively fuck around with the results.
It would be easy (and perhaps fun!) for me and anyone else reading this to inject doubt into this assertion.
I'm happily open to additional illumination here, particularly as far as a practical daily use review system.