Is this wheel built incorrectly?
It's a little bit wrong in that it has zero upside and one potential downside, but that downside is unlikely to ever be relevant.

Trailing spokes straighten a little temporarily under drive load, and this causes the spokes to essentially be pushing on each other a little at the cross. On a wheel laced like this (there's no agreed upon term for it but let's call it "asymmetric"), the idea exists that the forces from the spokes pushing on each other in this way add together and can cause the rim to get pulled over to one side slightly in use, whereas with mirror-image lacing the forces would cancel each other out, or come closer to it.

This is probably a real thing that happens, but it doesn't really make any difference I've ever seen, and we're talking about a very small amount of movement in the rim. If there were consequences, it would probably be on a bike with tight tire clearance. Some wheel manufacturers make all their wheels this way, because it can save steps and/or simplify their procedures. 

The more potentially consequential side to rebuilding a wheel this way is that double-grooving the flanges increases the risk of flange failure and increases the amount of work you have to do to get the spokes bedded into the flanges. So barring situations where you're forced to use a different lacing pattern on the same hub, or where you're switching to a rim of different "handedness" than the old one (only really something you'll see if vintage parts are involved AFAIK), there is zero reason to not re-use the existing grooves. (Note that this is not to say that flange failure is at all likely from double-grooving a tangentially laced wheel, just that the odds of it happening go up.) If the wheel was built asymmetrically originally, it should usually be re-laced this way.