I think there are a couple of things to possibly consider here:
Maybe this wasn’t the customer’s first iced coffee with syrup?
Iced coffee is typically a coffee made with less water than normal and ice used as bypass, as well as to chill the brew. This makes it prone to under-extraction, which will shift the flavour balance. I’ve never understood this practice really, with most other iced drinks it is accepted that the ice further dilutes the drink and everyone manages to cope with that just fine.
The shop obviously caters for this kind of drink & customer and seems to have dealt with it very well. If you have to remake a couple of drinks to ensure the customer keeps coming back, then everyone’s happy going forward.