Not sure what it's like nowadays, but 5 or so years ago, GC were very proud of being able to scale from 0 to a million users pretty much instantly. [0]
At the time AWS needed pre-warming. I've not needed to do that since, so I'm just assuming AWS solved that one (or everyone moved to serverless).
Obviously that's not the same as overall capacity, but the AWS good, everyone else bad rhetoric needs challenging sometimes.
Ouch.. that was a long time ago..
0: https://www.forbes.com/sites/reuvencohen/2013/11/26/google-s...