this is ment for players that go AFK cause they dont get what they want. NOT I REPEAT NOT !! for a person that needs to restart his router...
This is a common misconception. Leaverbuster isn't only for those who leave intentionally, it's also for those who have frequent internet/computer problems, or anything else that might cause them to leave many games. The fact of the matter is it doesn't really matter why someone leaves, because they still left and it can cause problems for their team since they need to fight a 4v5. Those with internet/computer problems ruin games just as much as those who intentionally leave.
Also, note that I said "frequent" problems. This is because Leaverbuster has some built in leniency. Riot knows that sometimes stuff happens, and sometimes it's out of our control, so LB doesn't punish because of one or two leaves, but rather when someone shows a pattern of leaving/disconnecting from multiple games in a short period of time. Because you have a punishment, not to mention the 20 minute punishment which is the harshest punishment LB gives out, you have show this pattern of leaving/disconnecting from multiple games.
All of this said, there could be an argument made to where if someone leaves but reconnects, and possibly even helps win the game, the leavers' teammates could vote on if they should be punished for it, but that's up to Riot to implement, and as of right now, that is not something apart of LB.