It is not a coinflip as long as teams not playing on the same level, it's just def 1-1 and decider being played. Does this impact some outcomes? Yes. Is this a big deal? No, especially when qualification/elimination matches are BO3. The main point against it I see on HLTV is "bbbut oUr tiEr OnE tEaMs are llliminateeeed cUz oF thaaaat, weeeee dOnT waaaant nEw FaCes weeee waaaaant only karrigan, cadiaN, Niko, s1mple and ZywOo" crying again and again.
I was skeptical about BO1 for a while and thought Professeur is wrong when he praised it, but after Rio and this major I changed my mind, it is the most exciting format and it not hurts the outcomes significantly as long as there are B03's afterwards. If team is good like Liquid or GL they are able to comeback, if team is bad, nothing will save it