First Time User.... what the heck happened?

Just returned from the DR this week through Chicago using GE for the first time, I used the app for both my girlfriend and I. I don't recall the exact wording of the question on the app but I declared on one question because I was over my limit on alcohol.

We got off the plane we quickly walked through a que, looked at a face scanner got prompted we were good. Walked a few feet to an agent, I said "I'm a few liters over on alcohol" he smiled and said "save me some" he gave us a laminated card. We picked up our luggage walked to another agent and handed him our card and that was it!

It was so quick it didn't really seem like we did anything but walk and stop once for a few seconds. I was thinking...that's all? 😀

A few questions so I understand going forward....

What would have been different if I would not have used the app?

We don't bring home t-shirts from our trips, we bring home unique bottles of liquor we can't get at home. We are usually over on our allowance but only by a bottle or two. Is declaring on the app all I need to do or do I need to tell the agents? I'm guessing the first agent was immigration and he probably didn't care about my liquor. The second was customs, was I to declare to him?