Yeah for me it's a bit unclear when you get a default loss and when you only get a minor warning. In my opinion teams should always get a default loss because if you only get a minor warning, teams will just accept that and have a higher skilled player play if the match is important (to carry them playoffs for example).
You can say the same thing happened in mid, but this teams only got warnings (2 major warning, so -3 points but they still made playoffs). They had to win the last game to make playoffs, so they played with 2 players that played in a higher div (http://etf2l.org/matches/75076/). And this wasn't the first time, they also broke this rule the week before (http://etf2l.org/matches/74934/).
I don't understand why Surstromming got a default loss while this team only got warnings. The last game is pretty similar to LR vs Surstromming, because it was the last game to decide who's going to playoffs, and both teams used higher skilled players to get the win. At least it's pretty clear in my eyes that if you give teams warnings they can just tank them and not care.