It seems to me that the CBP agent was unclear that the laptops were purchased in the US. A commercial good in the basic terms is something that is imported, as these were not imported they shouldn't have been considered commercial goods. What does make sense is that the agent saw the four newish looking computers and assumed that they were bough on your trip abroad for others use in the US which would then in fact make it a commercial good. Things start to look fishy if one person is bringing in four similarly looking laptops which might explain "the talk."

In the future to avoid confusion when carrying multiple computers it helps to bring receipts or evidence of the computer being purchased in the US, might be hard in this case with company provided computers. There are also forms on the CBP website you can fill out ahead of time.