Ouch. It's hard to tell from the pictures w/o seeing it irl, in the sense that you do need a void to compress the column, and the expansion plug typically has a lip that sits above the steerer, but it does look too short. Intellectually, i agree that you would expect the second bolt to be tightening over an area with steerer, not just void. Not hard to imagine a horror scenario where the stem / bar just pops off the steerer because 2 bolts work, but 1 bolt doesnt.