No, I'm sure they could have accepted any Hangouts call or being coerced into accepting a phonecall as well.
But truthfully what they wrote in the sendout was like I described - they outlined the procedure to go get the netbook and use it and at no point did they suggest a physical phone number to call or similar. I went along with it as far as I did just because I was kind of baffled by the suggested procedure :)
I assume it was part of some marketing scheme to try to market Hangouts and/or Chromebooks (or whatever it was) at the same time as GCP, but it just confused the sale and added unnecessary pain-points. The AWS guys just send an email and let me call them by a normal phone.