Ahhh the old "it's your faulty playing technique" response from the guitar tech who did the set up. I've heard that one before too - but did not fall for it. You should not have to alter otherwise proper playing technique to get your guitar to play buzz free. Sometimes positioning of certain phrases you play will necessitate placing your finger farther away from the fret. All strings should be equally buzz free.
If the fret buzz is isolated to the D string, then most likely the set up was in fact done almost properly.
Fret buzz occurs when the vibrating string (which actually oscillates in a circular pattern vs. only back and fourth or up and down) contacts the fret creating a buzz. This can be a result of action that is too low, a fret that is too high or an anomaly in the neck that causes certain sections of the fretboard to end up closer to the strings than others (twisted neck or warped neck or bump at the neck body joint).
But if any of these things were going on - it would likely cause fret buzz on more than just the D string.
So I believe that your guitar has most likely been set up with the action as low as you can get without all the strings buzzing. Yet for whatever reason, you are getting a buzz on the D string only.
If you otherwise like the guitar, before you take it back, try these ideas.
Try a different gauge string. A slightly larger diameter (heavier gauge) string would be less prone to buzzing and it may solve your problem. A slightly heavier gauge string will require a tad more tension to tune to pitch. Moving your fretting finger closer to the fret also stretches the string a tad more than fretting in between two frets. Since that seems to take out the buzz, my guess is you don't need anything more than a very slight increase in tension to eliminate the buzzing.
You might also try a different brand of string on the D string of the same gauge you have now. If the string is made with a denser composition, it may require just a bit more tension to tune to pitch. I have personally done this with one of my guitars on the G string and changing brands took out the buzzing. You can order individual strings from Just Strings - Single String Page
If you prefer not to use a heavier gauge string for your D string or don't want to try a different brand, you could go back to a guitar tech (perhaps a different one) and have them adjust the set up for a slightly higher overall action to take out the buzzing on the D string. Your guitar appears to have a two way adjustable truss rod so it should be possible to make the needed adjustments to eliminate the buzzing.
Be sure to get the issue solved to your satisfaction before the return period expires. Your guitar should be a source of pleasure and enjoyment, not frustration! Good luck.