You are both right. With unchanged demand for imports, then the total value of imports in USD would be the same, but a stronger dollar would affect the relative

You are both right. With unchanged demand for imports, then the total value of imports in USD would be the same, but a stronger dollar would affect the relative demand for imports vs domestic commodities in reality given basic supply and demand assumptions. But the point is still correct that you would have to adjust for the relative change in currency prices to know whether the amount of stuff we are taking in from abroad has really changed or not.