Whenever I ask a question regarding sublime text, I always include all three of these tags in order to attract the attention of anyone who has any one of them subscribed. This is because the programs are so similar that it is very often not important what version you are using. And I could easily see people writing "In ST3, you can use..." for questions tagged ST2 because that is a useful answer; if not to the person asking, then to future readers.

I agree that I'm likely using the tags incorrectly this way, but it also feel wrong to not include one of them because it's an easy way to get desired, useful attention.  Are the three different tags truly necessary? We don't have tons of version tags for other programs; see http://meta.superuser.com/questions/4532/firefox-versions-going-to-infinity-should-we-merge-the-tags