The 2 door wall cabinet is never built with a center support. If you order a 48″ wide unit, you will have a full 46.5″ wide opening behind the doors. If you prefer a center support, simply order two separate single door wall cabinets and attach them together.
Keep in mind that cabinets over 36″ wide are considered fairly large. Shelves can begin to sag under heavier loads, even though they are made from 3/4″ plywood. They won’t fail, but some deflection is normal at wider spans.
If this becomes a concern, you can double up the shelves by ordering extras and stacking them, or add additional support along the front edge as needed.