Right, the risk structure presumably protects the vendor if just one customer sues, even if the amount of damages claimed is astronomical. Because vendors try to disclaim bet-the-company liability on a single contract.[1] The vendor's game is to make sure the rest of the customer base does not follow this example, because as noted in the linked article while vendors don't accept bet-the-company liability on each contract (or try not to), they do normally have some significant exposure measured in multiples of annual spend.
The assumption is not only perfectly valid, it's the very reason such contracts are signed in the first place! It's what companies want to buy, and it's what IT security companies exist to sell.
Yes, I know that's what everyone wants/thinks, but you actually can't do it. Because at the end of the day, you chose the vendor. So you are still liable for all of it.
[1] https://www.gs2law.com/blog/current-trends-in-liability-limi...