I think it depends on what the person who estimated the service time to 2 minutes had in mind.
A service is a part of a transaction, which includes more than just the service. Config validation and pushing config to a device are examples of steps in a transaction that can take a while. So if you want to know how long it takes from the point when you commit a change to NSO until the changes are pushed to the network, then you have to include all the steps of a transactions in your measurements. That includes service create callback, pre-mod, post-mod and and everything else within the transaction.