Dr. V versus Alisdair MacIntyre

Dr. V's latest Substack continues his meditations on the ability to logically derive ought from is, something that the Scottish philosopher David Hume said was impossible. Can one logically deduce the normative from the brutely empirical? 

Dr. V shows us a passage from Alasdair MacIntyre in which MacIntyre seems to think that such a derivation is possible. According to MacIntyre, any watch is by definition already a good watch since the function of a watch (a good watch) is to tell time accurately. But Dr. V counterargues that accuracy is a normative, not empirical, concept, so if MacIntyre seriously thinks all watches are good by definition, then a slow or otherwise inaccurate watch is not even a watch, which is ridiculous. Go read Dr. V's article here.

But here's the portion of the first part of Dr. V's argument where I have questions:

The correctness of the argument is supposed to hinge on the functional character of the concept watch. A watch is an artifact created by an artificer for a specific purpose: to tell time accurately. It therefore has a proper function, one assigned by the artificer. (Serving as a paperweight would be an example of an improper function.) A good watch does its job, serves its purpose, fulfills its proper function. MacIntyre tells us that “the concept of a watch cannot be defined independently of the concept of a good watch . . .” and that “the criterion of something’s being a watch and something’s being a good watch . . . are not independent of each other.” (ibid.) MacIntyre goes on to say that both criteria are factual and that for this reason arguments like the one above validly move from a factual premise to an evaluative conclusion.

Speaking as someone who has been more influenced by the moderns than by the ancients, I don’t see it. It is not the case that “the concept of a watch cannot be defined independently of the concept of a good watch . . . .” A watch is “a portable timepiece designed to be worn (as on the wrist) or carried in the pocket.” (Merriam-Webster) This standard definition allows, as it should, for both good and bad watches. Note that if chronometric goodness, i.e., accuracy, were built into the definition of ‘watch,’ then no watch would ever need repair. Indeed, no watch could be repaired. For a watch needing repair would then not be a watch. No one denies that a good watch is an accurate watch. The question in dispute is whether the normative property of accuracy enters into the definition of watch. [emphasis added]

My question in return is: Why is accuracy a "normative property"? Can't accuracy be objectively verified? Isn't accuracy therefore factual/empirical? 

In science, there's a distinction between precision and accuracy as relates to instrumentation. Let's say I have a lab scale that can measure weight down to the microgram. That would make the scale a highly precise instrument. But let's say I misuse the scale and weigh an object incorrectly because I calibrated the scale incorrectly. The resultant incorrect weight would therefore be an inaccurate measurement. Precision is more a function of the instrument; accuracy is more a function of the user. If we move into the domain of sniper rifles, we can see this even more clearly. If I have a sniper rifle that's precise to a distance of 3000 meters, then I take a shot and miss my target, that's because my shot was inaccurate. Whether we're talking about the lab scale or the rifle, where does normativity come into play?