I'm just looking at it from the perspective that almost all of Ukraine's neighbors to the west are NATO countries. Belarus is to the north of the region you are talking about for incoming logistics. That means Russia has to either actively involve Belarus or an air strike would have to cover a lot of Ukraine, and Russia doesn't have air superiority. Does Russia actually have other weapons (missiles, cruise missiles, drones) with the accuracy to hit targets over that distance, and would countries like Poland see the strikes coming their way and just assume they are supposed to hit Ukrainian targets near the border? Looks like risky business where the incoming weapons and supplies are still concentrated.
In the past we and other NATO countries have had a lot of surveillance planes flying near the Ukrainian border that you assume are looking at what's flying over Ukraine. BTW ADSB isn't showing anything there right now which doesn't mean they aren't there, but there is an RC-135 Rivet Joint cruising the China coast from northwest of Okinawa down to Taiwan and back - flying out of Kadena - Okinawa.
