I haven't personally tested this.
But after over a week of streamers looking for convoys, I haven't seen a single one yet to find more than a single wreck at a convoy event.

Maybe they were starting to despawn right as the player entered the cleanupradius

Just seems more than coincidence now. I see the config is the same as stable chernarus, so shouldn't be different other than the assets..
I think most of these were found on the More Cars server.

Find Convoy