For proper English, it should have a capital B there. All other Boots in the game follow this proper naming scheme, this one has had a lowercase b in it since it was introduced back in Patch 3.4
They're lowercase on the Lodestone for proof: https://na.finalfantasyxiv.com/lodes...m/d655a69b179/
EDIT: This was fixed in Patch 5.21, thank you!