Could just be an oversight on the part of the CGI department.
Think it mentioned in the RDM invterview for the final (linked in the relevant thread) that the Earth from Crossroads wasn't supposed to have clearly identifiable land masses to indiciate whether it was our Earth.
The ideas now the series has finished that the Earth of Crossroads was the Earth of the 13th Tribe but not
our Earth in anyway, shape or form. Where the Colonials have settled (our earth) it to them Earth Mk II