The workflow would usually be that the server takes your card and enters a transaction with the non-tipped amount into a machine. This authorises a transaction and prints a receipt for you to sign, and optionally(*) to add a tip. So Mondo gets a first transaction for the non-tipped amount. You then hand write a tip and the total on the receipt and sign it.
I could imagine that in many establishments there are only a few members of staff who are allowed to update the transactions with the new amounts (with tip included). Bear in mind that the customer does not get a new printed receipt with the updated amount, so the bank is trusting the amount entered by the restaurant to be the same as what was hand written by the customer. (Errors in the original entry would presumably be caught by the customer as they sign the receipt). Also, if tips need to be totalled and allocated then it might be safer to restrict the number of people who are able to enter them. Once this is done Mondo will get an updated transaction.
It’s clear that there have to be two transactions, and I think that there are good reasons for the second one be done later.
We could all hope that the US adopts the European approach of bringing the card reading machine to the table and allowing the customer to enter the tip directly … resulting in a single transaction … but this seems to be very far away.