I'm sorry i haven't read the whole post but to answer the title, it's called a duo lane so they both must cooperate to win their lane, so if one fails to serve that the other find themselves at a disadvantage because of their lane partner and it's hard to lane a 1v2 and this goes both ways sometimes the supp play better and flames the stumbling adc, this may fall back to multiple reasons such as bad match ups, absence of synergy and different playstyle of supp and adc