I'm not certain this is a bug at all, and I was hoping someone could help confirm one way or the other:

I set my speech skill to legendary, and it seemed to work. My perk points were returned, and the skill was set to 15. However, to my surprise, I encountered a shopkeeper I hadn't invested in yet. Which I only noticed because he had a dialog option for investing in his business.

Which leads to a question, is this a bug, or am I misunderstanding how the legendary skill feature works?