The Google part of the name means that the service could be shut down at moment's notice if it isn't providing millions of dollars in revenue and even then it's a toss up if the people in charge get bored of it.
Google Cloud isn't someone's side project though so the risk is much lower. You're right that services can be shut down at moment's notice but that applies to any service of any kind. Unless you host with multiple cloud providers at the same time you cannot avoid that risk.
The petty snipe is not necessary or appreciated.
Google has a terrible reputation with consumer services but has been pretty decent with Google Cloud so far. The biggest negative example would be Google Maps pricing changes but that seems to be different class of issue.
There was also a similar one for Mozilla: https://killedbymozilla.com/
Perhaps they were being weary due to the practices the entirety of the company has displayed in the past, in regards to killing off products.
Not sure about Google Cloud in particular, though.