Delta Faucet: Maximum Gallons Per Minute with New Aerator
This faucet comes from the factory with the Delta RP61340 aerator which is a 1.5 gpm aerator.

This would mean that the faucet's internal valve and/or water delivery configuration is what limits GPM delivery to 1.2. So... NO, replacing the aerator won't help you because it comes with a 1.5 but is certified at 1.2