General question: What exactly is considered a good reason to request tag aliasing?

Specific scenario: I just discovered that while Danbooru had recently aliased [[artoria pendragon lancer (fate/grand order)]] to [[artoria pendragon (lancer)]], Gelbooru has yet to do so, and a few recent uploads (which, IINM, are imported directly from Danbooru) use Danbooru's new tag. Does Danbooru doing its own tag aliasing qualify as a sufficient reason to do the same here?

PS: While I'm personally interested in resolving the specific scenario, I'm also interested in the more general subject.

It's very rare for us to actually approve hard aliases. The alias system itself and alias approving works fine, but breaking an alias requires rebuilding the search index, which can take the site down for anywhere from a couple hours to a full day, so we generally only approve aliases if we're certain that we won't want to break it, and when it comes to name qualifiers that's never the case.

Moderators do have the ability to perform mass tag edits to switch the tag on existing posts. If you find any similar tags in the future, please request a mass edit on the Gardener's Guild thread, located at forum #1706.

Duly noted, and thank you for responding so quickly.