I'm clearly not part of the conversation you two are having but I would like to clarify one thing, so I'll join in on the hi-jacking
39"x21" is significantly smaller than a 2x3 CC cage. When we say 2x3 we are talking about grids, not feet.
Since Target is pretty much the main supplier of cage grids for people we should be looking at what their grid sizes are.
Cage grids are minimum of 14" square. That makes a 2gridx3grid cage
29.5" (with 1/2 inch per connector added) or 28" if you don't use connectors. for the width it's 44.5" length (again adding the additional inches for 5 connectors) or 42" without connectors Using those numbers, I get
9.11 square feet with connectors and 8.16 square feet without connectors for a 2x3grid cage.
Do folks assume that grids are one square foot when they see people use the term "2x3" and assume we are talking about square feet (as in 2'x3') and NOT as in 2grids X 3grids?
I don't know where those numbers on the home page come from but I do know that the cage on that link you are talking about is significantly smaller than a 2gridx3grid cage which I can tell just by looking and I don't even need to calculate that one.