[Boulth]

This is not entirely correct. It's not Bazel but "build system very similar to Bazel" (from your source) and that's I guess their internal Blaze tool.

I wonder what's the real usage of Bazel (not Blaze) in Google.

[karlding]

According to this comment [0] by laurentlb (one of the people working on Bazel who also commented in this post) from a year ago, Blaze is just Bazel but with integrations to Google-internal tools.

[0] https://news.ycombinator.com/item?id=18823546