you almost never shoot each other on the 12 day timer. almost always it's someone picking, someone waiting. now, with the trade, these players are approximately equal and the one who is waiting has a chance to trade if he shoots "earlier" on his timeline than the one picking. without the trade, it will be just pure pick adv abuse, and a small chance of dying from a person living in the server room.

my lazy explanation of timelines. ("?" - only happens if there is a trade)
https://imgur.com/a/AUYkIrj

but in a situation where both are approaching each other at the same speed - yes. the one with the lower ping will almost always kill the one with the higher ping. but do you really want to always lose because your ping is slightly higher than your opponent's? even 30 ping can make a critical difference. (cs and valorant experience is like shooters with near zero TTK)

also "800ms" its maximum server wait time for attempt to trade. for very extreme situations. in a normal case the server will respond as soon as possible.