Owning an NFT, such as The Greedy Machines series, means that you have a unique, digital asset stored on the blockchain. This asset represents ownership and proof of authenticity of that particular NFT, and it can potentially have value based on factors such as scarcity, demand, and utility.
The description that you've just give isn't different from the other NFTs that has been launched in the market. All of them gives you ownership and authenticity that you own them and of course through buying it.
In the case of The Greedy Machines, these NFTs are backed by real computing power, which can allow the holder to earn BTC through mining. Additionally, the power of each NFT can grow as new collections are issued, and holders can participate in game functions through their personal account on the "Mining Farm" page.
Seems like a cloud mining and is just using the sales of the NFT. So, for the devs it is one stone hitting two birds at the same time. I've seen projects that do have that feature and didn't managed to stay long.
What other earning opportunities do you know?
Mining(real), trading, holding, etc.