It's not an exploit. I believe in an effort to encourage competition over buffs (less at the start and more during the match, the Lichenweed map connects along the "back" route behind the large tree. If someone's fast enough and bypasses their own, they can attack the enemy team's boxes and prevent them from being able to grab their buff. But in doing so, they are effectively throwing themselves at the enemy team early on. Simply put, if you see them coming, CC or KO them and then take your buffs.

I also think there's a bit of local meta mentality at work. Perhaps non-US players are less likely to attempt to sabotage the other team, and the map design permitting buff stealing was an oversight? For obvious reasons, I can't say this with certainty, but after watching some of the matches at Fan Fest, I noticed things play out VERY differently in other regions.