Is this actually safe?
Well, it's kinda the point of having artifact versioning. Presumably, Google intends to keep those older artifacts around in your local Google Repository.
If you're seriously nervous, back up your developer machine. (and if you're not seriously nervous, also back up your developer machine) You can always rummage around an old backup to grab the artifacts and cook up some means of using them in your app.
I.e. is it downloading/building the actual older version of the API?
It is compiling into your app the JARs/AARs that represented the Play Services SDK for that version. It's how all artifact versioning works. If you go to your Android SDK installation, and look in extras/google/m2repository/com/google/android/gms/
, you will see the various artifact names. Go into those directories, and you will see the versions. Go into a version directory, and you will see the files. Go into the files, and you will see the bits. You can try diving down into the bits to see electrons or something, but I think that'll be carrying it a wee bit too far.
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