As others have said, I'm pretty sure the "5+" is just there so people wouldn't worry about whether someone with a Virtue at 6 could take it. I'm glad they did, as it's going to become relevant for my Zenith at some point (well, not precisely this Charm, but a modified version based on the Sun's virtues using this one as a balance point). Because getting 6 automatic successes every time you roll your Cursed Virtue is the best idea, especially with Glory to the Most High
... I should probably pick up Truth Shines Through before GttMH, come to think of it.