Special Abilities, like RCN, you either have or don't have. A unit can't have it twice. Values can be increased or decreased (SRM1/1 versus SRM2/2), but RCN doesn't have a value. You either have RCN or you don't.
Battefield Intelligence Rating Table says "each ground unit with the RCN special ability". Even if you could give a ground unit RCN twice, for BI you still wouldn't have changed the number of ground units with the RCN special ability.
But BI is written that way because RCN is a toggle, yes or no, not a rating like SRM. It is written that way because you can't have RCN twice on one unit.