One of the top things I hate about this game is your Promotion series.
There's so many ways to get screwed out of them.
First of all, Riot says it's a required 2 out of 3. It's actually a required 3 out of 4 with the first game a required win because you need to win a game to get into your promos anyway.
Same goes to a 5's series. It's not 3/5 it's actually 4/6 with the first game a required victory because, again, you need the first victory to get into your promos.
Promotion matches are just inherently toxic no matter how you look at them.