The Honda Type 2 Coolant contains "NO Silicate and borates," and that is the key. What they probably used was the cheap Prestone from Walmart. Now, that's a pretty good coolant nowadays, but the chemical composition is slightly different. Will it have an impact? Hard to say, probably minimal. Your biggest risk is warranty compliance, but seeing as how you're driving a 2002 Civic, it's unlikely a concern.
Search the MSDS sheets to see the contents of the coolant. Note that the Prestone doesn't appear to have the KOH and it's unclear about borates restricted in the Honda fluid:
Honda Type 2:
- Ethylene Glycol 47-53%
- Diethylene Glycol <3%
- Potassium Hydroxide <3%
- Hydrated inorganic acid, organic acid salts <5%
- Bittering agent >30mg/kg (Added so you don't eat it)
Prestone 50/50 prediluted engine coolant:
- Ethlene Glycol 45-55%
- Diethylene Glycol 0-5%
- 2-Ethylhexanoic Acid, Sodium Salt 0-5%
My recommendation is to not worry about it because the vast majority of your coolant is still the Honda Type 2 and the little bit they added to top it off is not going to vastly change the composition of your coolant. For other maintenance reasons, you may want to consider draining and refilling your coolant on a car that is 17 years old as that itself will likely prolong the life of your cooling components. In that case, just get the right amount of Honda Type 2 and take it with you to the shop.
The experts we spoke to at SAE (the Society of Automotive Engineers) said that you can mix up to about 15 percent traditional coolant in your OAT coolant before you have any real effect on the corrosion inhibitors.
More generally, why are coolants different? The composition of these chemical compounds is based on Society of Automotive Engineer requirements to maintain the viability of internal engine components. As there is a range of manufacturing metallurgy and composite components in the world, there is a range of antifreeze requirements.