A good one. Having the subject on the left, and the negative space on the right sets up an interesting dynamic.
When it is reversed, when the negative space is on the left, we quickly move over to right, pause on the subject then off the frame. Once you set the eye in motion it tends to stay in motion (Newton's first law of inertia). A vase of flowers is not unexpected enough to stop the eye's motion for more than a beat. The eye might return to examine the flowers more closely, but you've squandered two seconds of the seven seconds typically given to a painting.
However if, as in this case, the subject is on the left, and negative space on the right, then there is no reason to scan, we've found the subject right off, the eye is captured and spends the full majority of time examining the flowers..
There are compositions where the negative space has interesting details, pathways, etc and we want the eye to first discover before landing on the "target" in those compositions not having the subject on the left has advantages.