So, when does a (grid) puzzle genre have its own tag?
Ideally, tags are not there to slap a label on everything - they exist to help in locating content of a certain type. If there aren’t enough, say, fillomino posts (I found just 4 questions) to indicate there is particular interest in that type of Q&A, then it’s probably reasonable to guess that there aren’t many people who would be much bothered by the lack of tag as an easy way to sort and target them by.
Tags, being user created, tend to appear when they’re wanted — and in particular, when there’s a sub-community that has a particular interest in that subject. If the people who are interested in a specific type of puzzle haven’t found it to be a problem that there’s no tag for it, then we probably don’t need to create one just because.
I’d venture to say there are people who are interested in Sudoku specifically but not all the other grid deduction type puzzles. This makes a good case for having a sudoku tag. Same for mastermind. I’m less convinced there are deeply devoted minesweeper fans, but there are 24 questions on the site and 5 for the last year so what do I know :) These are puzzle types most people have heard of even without having a particular interest in puzzles, so having tags specifically for them makes good sense.
Beyond that, it starts getting less likely that a specific subtype of grid deduction puzzle has a particular need for its own tag exclusive of the others or of the general type. The partiti tag was on exactly one question and never should have existed (I’ve removed it, and that tag will vanish soon). slitherlink is probably warranted, and the nonogram tag has 39 questions in it (15 this month, 27 this year) so there is current activity and interest in this puzzle type. Other types, not so much. Kakuro I found just 10 questions, akari just 4.
People usually post here when they think a new tag is needed, and we do a quick look to see if it makes sense. I think right now our tagging situation looks pretty good for these puzzles - we have tags for the types that would be most likely to be of specific interest, and a general tag for the genre; searching for a less common type by text will find those if one is looking for a given subtype. If there is a specific tag you think we’re missing and is needed, propose it and let the community weigh in on it.