You understand it if you think of engineering infinites rather than mathematical infinites. The capacity of a full single datacenter can be treated as infinite for most customers. I explained how its defined in the original comment. Amount of places in engineering where you treat even a 3 order of magnitude difference as infinite is a lot, but the number of order of magnitudes varies depending on context.

Maybe if you're the only customer, but it seems you've not yet gotten a "no capacity" error from AWS, which happens sometimes.

You don't have a single Google datacenter (or any other provider / big name) for a single tenant. The bigger the DC, the more the number of tenants/customers reaches "infinity" (giving the same meaning to "infinity" you are giving to it)

No customer has access to an appreciable fraction of any data center, and if they do they don't have 10x overhead in reserved quota.

It is infinitely larger, because there is no distinction between more than you use, and infinity.

Sure there is infinite capacity given an infinite amount of time to scale up. I assert you’re leaving out the time dimension. Those so-called infinities are simply not accessible in a practical way since you’ll hit a wall in actually provisioning that capacity long before the data center runs out of compute.