My hunch is they need more than the Roseville chargers will support, and this site is also just off I 80 and soon to be mostly solar powered.
Yes my guess is that they can't easily being in more power to the Rockville SC site so decided to build a new SC at a site they have more control over and with readily available power, the Rockville Service Center.
Exciting to learn that it will have PV panels! But they won't make it "mostly solar powered": the PV coupled with batteries appears to be for peak shaving and power management.