Single bullet points are aurally messy. So unless LibGuides forces you to do it (i.e. putting in a hyperlink), only use them when there are multiple items.
When screen readers read a bulleted list, they announce that it's a bulleted list at the start, each bullet point, and when the list ends. For an example, let's look at a grocery list:
- milk
- butter
- ice cream
- apples
This will sound something like, "begin bulleted list bullet milk bullet butter bullet ice cream bullet apples exit bulleted list".
A grocery list with only one item
sounds like, "begin bulleted list bullet milk exit bulleted list". It's hard to find the meat of that, especially since the screen reader has no emphasis or change in tone.