I read it as site size more than anything else. They have three...

I read it as site size more than anything else. They have three different sites in Sudbury with a preference to one. They went on about infrastructure all being in place etc. Then mentioned the size ie one football field.
My take is that a phase 2 plant will take considerable more effort to bring to fruition.

Scaling up to a full size plant requires at least 7 times the area and a lot more investigation. By having phase 2 separate, will allow phase 1to fully function independently while construction is taking place, and continue to do so through commissioning.