I have seen quite a few tag wiki excerpts in the edit queue that start with "Questions related to".
Do we really need this sentence? Isn't it redundant? It describes a tag of a question, isn't it obvious that it describes what the questions are about?
No, they don't.
and some already don't such as theresa-may for example.
Theresa May is the current Prime Minister of the United Kingdom. Use this tag with the [united-kingdom] tag
I'm pretty sure nearly all of those were my suggested edits, I just used other excerpts as an example and it just became a routine from there. But it's pretty much personal preference as @Carpetsmoker mentioned.
I wouldn't edit it just to take that away though because you feel it's redundant, you'll run the risk of being rejected. It doesn't take anything away from the excerpt itself, nor' does it add anything. But if in the future you're suggesting tag excerpts by all means, don't add it in.
The main argument in favor of it is that people who are unfamiliar with stack exchange may not understand what tags are. The tag wiki excerpt is intended to guide people in using tags, but a common approach from outside is to make them into dictionary style definitions. Formulations like "Questions related to" push people back to describing the questions rather than the tag's subject.
This doesn't matter as much on a site like Stack Overflow, where most of the tags are already filled and where tag editing approval is a high privilege activity. But on a beta site, it's much easier to find empty excerpts and to get the privileges to edit and approve them.
