These sorts of details always distract me. At this T intersection, you only have two choices; you can turn left from the left lane or go straight in the right lane.
It appears this sign said “ONLY” for both lanes at one time, but then the decision was made to cover the ONLY under the right lane with matching reflective tape (hard to see in the picture).
It’s unclear why. Your only option in that lane is to go straight, so the original ONLY was accurate. I’d speculate that at some point a rule was changed so that only turn lanes can have ONLY so that it becomes a subtle secondary queue that you MUST turn if you are in that lane.
If that were the case, then the state would have three choices: replace non-compliant signs, doctor non-compliant signs, or ignore non-compliant signs until they are eventually replaced (which could be a very long time). When weighing cost versus benefit, apparently the middle path won.
It seems like we are making these kinds of decisions all the time. Last year, RSM went through a rebrand, which created the need to rebrand thousands of training-related documents, some of which we rebuilt, some we kludged, and some we ignored (and are still ignoring until we have cause to touch them).