I think it's the terminology because it will work directly between the two blockchains and not via an exchange. That's what I understood from their post:

This would be the first time in history that two blockchains of this size will be connected to one another so that tokens can flow freely, and voluntarily, between the chains without the need for trusted intermediaries like exchanges.

If we ignore the first part regarding being the first time, which might or might not be accurate (they do say "of this size" and I'm not familiar of the sizes of the other blockchains which inter-operate), they do say one very important word - VOLUNTARILY. No one will be forced to do these atomic swaps if they don't want to, which seems much better than the sound of the initially marketed token swap.