Users Signing Up With First and Last Names

We had previously customized the text in /admin/customize/site_texts, but I was not familiar with the full_name_required setting. So I set full_name_required to true, and I can’t tell what good it did, except to overwrite our customized text. What is it supposed to do? I thought it might at least require two words in the profile > Name, but I can still edit my Name to just “Mark”.