Providers often just ban all crypto mining. I think it might be because of pressure from authorities fighting money laundering.
Source: Worked at a cloud infra provider that struggled deeply with this problem.
Generally speaking you're not going to get banned unless you spin up max quotas and have other signals for fraud, such as zero payment history, connecting from regions with high fraud rates, etc. More often the provider will just limit your resources - either openly, like AWS does, or more subtly.
Unless that's exposed to the customer (AWS burstable instances are actually okay IMO), that sounds like the cloud provider committing fraud and hoping nobody calls their bluff.
> Any act of deception carried out for the purpose of unfair, undeserved and/or unlawful gain.
(https://en.wiktionary.org/wiki/fraud#Noun)
Is the cloud provider getting money off of this arrangement? => Yes, obviously they're getting paid here.
Is the cloud provider getting that money as a result of deception? => Yes, by selling ex. the use of 1 CPU core when they actually have no intention of letting you use that core. Now, I'll grant that in an actual legal case it might well be possible to get away with this by burying it in the ToS, but this is HN, not a court room, so I'm comfortable setting the bar at "would most actual users expect that to happen based on marketing?", conclude that no, most users would consider that surprising even if there's something buried in the ToS claiming that it's allowed, and call a spade a spade.
the worst part is that there's somebody in a GCP office somewhere that might secretly believe that I'm actually a cryptobro. shudder
you're probably safe on that front, it isn't like the GCP folks are paying any attention to the customers.
In either case (gym or GCP) you'll be entitled to a refund for the difference. They aren't allowed to just kick you out and pocket the difference.