Whilst it is great that they're able to include a container image for this, it isn't difficult to run a few commands to download Bitcoin Core. If you have to update Bitcoin Core in the near future, you would also have to do it yourself.
I agree that it's going to be easy but at least they could set it up for you if that's the goal of your VPS.
400gb disk capacity should not be enough for a full btc node now.
It is not enough, you can see the right side on the screenshot that it recommends to add more storage.
I do not believe that Contabo sets up a bitcoin node for you though - I think you have to do that yourself, and that they only supply suitable hardware for it.
Why don't you believe? It's already shown that an image is already prepared for launch. I think it would be setup already, probably have to add something before it starts, maybe the blockchain is downloaded or something once they have launched your VPS.