Why do the Borg call it that?
How many Sectors are in the Alpha Quadrant?
Wouldn't the Borg refer to Sector 0-0-1 as their own home sector? But they understand humans enough to call out their home region, even though fear is irrelevant...
How big is one sector?
The Federation existed before Earth joined up, so was a remapping or re-kerjiggering of sectors imitated at some point? As practice for stellar cartographers, the same way people shoot tin cans off of wooden fences to improve their hand/eye coordination acuity? Why not let the computers do the calculating?
The fact Picard is converted into a high ranking Borg drone and Earth is still called Sector 0-0-1 by Locutus... would the Borg really need to turn Picard into a walking demonstration of novelty electronic gizmo products found in bland shopping malls -- or more pertinently a locus o' focus for Borg intentions -- if they already have used human psychology as a relational reference point (like a security blanket?)
Even though Earth is not the epicenter of the Federation, or if it was moved there long after baking bread with Vulcans...
How many Sectors are in the Alpha Quadrant?
Wouldn't the Borg refer to Sector 0-0-1 as their own home sector? But they understand humans enough to call out their home region, even though fear is irrelevant...
How big is one sector?
The Federation existed before Earth joined up, so was a remapping or re-kerjiggering of sectors imitated at some point? As practice for stellar cartographers, the same way people shoot tin cans off of wooden fences to improve their hand/eye coordination acuity? Why not let the computers do the calculating?
True, it's to make the audience feel all claustrophobic and terrified via extension, but forgetting production reasons what are the more important in-universe reasons? 

The fact Picard is converted into a high ranking Borg drone and Earth is still called Sector 0-0-1 by Locutus... would the Borg really need to turn Picard into a walking demonstration of novelty electronic gizmo products found in bland shopping malls -- or more pertinently a locus o' focus for Borg intentions -- if they already have used human psychology as a relational reference point (like a security blanket?)
Even though Earth is not the epicenter of the Federation, or if it was moved there long after baking bread with Vulcans...