The following keywords will close an issue via commit message:
What's the difference? When better to use close or fix?
Basically, it doesn't matter. If you use Fix as a mark for a commit that makes the issue go away, then use that. The same applies for the other keywords.
GitHub only gives you more options, because it tries to strip you of additional work e.g. finding issues the commit might be related to and manually close them and to do that it uses more keywords that could mean close <issue>.