He addresses this scenario:

Let’s take another example, which is more like what actually happened in Q1. Suppose an American company, Best Buy, decides to buy a Chinese TV and put it in a warehouse, because it knows that tariffs are coming soon. That purchase counts as inventory investment. So investment goes up by $1000. And just like in the previous example, net exports go down by $1000. The two cancel out, and the total contribution of the imported TV to U.S. GDP is zero.