I'm not an expert, either, but the outlet temperature from the duct should be pretty much the same regardless of the outside temperature. It's just that there isn't enough cold air, not that the outlet temperature is too warm.
As I understand it, the system is designed to some load at which it can attain some desired temperature in the house. As the outside temperature exceeds that design load, it would gradulally fail to maintain the set temp. For example, if it was designed to be able to maintain the house at 73 with the 3T load at a 95-degree day, if it was 100, then the inside should only rise 5 degrees.
It might not rise that much depending on how much of the house was cold-soaked, and how long it was that temperature. this all plays into the proper heat load analysis and how oversized, if any, the system is. For maximum comfort, it is better to not have it oversized, as running contantly handles the moisture and comfort levels better.
If the ducts were blowing warm air, something is wrong. The compressor may have a leak, and lost some refrigerant. If the air flow isn't proper, things can ice up, restricting air flow.
I think he was blowing smoke...