D&D 5E Xanathar's for a specific setting according to Mearls

[gyor]

I read that as "you would need a bridge book for each setting, equivalent to a Xanathar's Guide (which is generic) but setting-specific."

Are people reading it as "Xanathar is for a specific setting"?

I gained greater context from a Jeremey Crawford tweet, so I no longer under that misunderstanding.