But only for challenges that relate specifically to features unique to Minecraft, and not challenges that were inspired by Minecraft/Minecraft features
Minecraft has a system of commands, as well as a method of mimicking electrical circuits via redstone. Through these, Minecraft is (close to) Turing complete, and we have answers on the site written in Minecraft. Questions about these systems, such as Simple Redstone Simulator or a tips for golfing in Minecraft question would be applicable to this tag.
Questions that are inspired by aspects of Minecraft, but that do not relate directly to the coding system of Minecraft should not be tagged with minecraft. In the same way that a question about printing the Jelly code page would not be tagged with jelly as it isn't inherently about Jelly, but a question about a specific feature of the language would be.
In short, if being about Minecraft is a central part of the challenge, not just an inspiration, then it should be tagged with minecraft.
...but maybe No
For similar reasons to how we declined the creation of an xkcd tag, there is no real classification that arises from having a minecraft tag. Just looking at the three challenges you linked, one is a parsing / string (YAML to JSON converter) challenge, one is a KC (compression) challenge, and one is a 2D string/grid scanning challenge, and the other ones have similarly unrelated tasks.
Tags are supposed to categorize challenges by some meaningful distinction, which this does not serve.
(Please upvote this to agree and downvote this to disagree. This is not a binding statement, just my opinion and an option to vote for.)