why does everyone assume TCP and some kind of reply or acknowledgement when considering these sorts of configuration options on switches? what if you're broadcasting over a network, and you only want to allow data to propagate one direction? it's not nonsense... it makes perfect sense, and it's a valid configuration, though it's not very useful for typical TCP IP networks. video multicast is probably the most common example of this being used, another is port mirroring for monitoring.

unidirectional broadband topologies are perfectly valid and have real use.

https://en.wikipedia.org/wiki/Unidirectional_network