That's not how modern ethernet works at all. A single NIC talking directly to an another one has no collisions ever. Depending on what your channel is, either you have separate wires for the directions, or you are using a hybrid circuit (as in telegraphs, the term is so overloaded it's hard to google). Either way, packets going in one direction never wait for packets going in the other.

But why would you? You don't have collisions since the introduction of full duplex ethernet on both copper/fiber. Kinda sounds like you're confusing half duplex with simplex, or maybe bidi? As a network engineer I've never seen someone ever refer to "simplex ethernet".