It really doesn’t matter to me with the first three examples, but it does with Sanctum Sprint and Southsun Survival.
Sanctum Sprint is especially bad, because it’ll often start you all the way at the beginning with enough time to get to the end, but you still don’t get a reward, even if you run the same race as everyone else. IMO, you should just get placed at the beginning no matter how late in the race you enter. If you don’t make it to the chest, you’re not going to get a reward anyway, but if you DO make it, you SHOULD be rewarded.
With Southsun Survival, once the death protection buff drops, the match should be closed to additional players until the next match. It is a waste of the player’s time to spawn into the game as a wisp and have the reward withheld.