Notice both of his ADC's KDAs. I believe this could be one of the symptoms of his play style, no? You bring up a good argument, maybe he was CounterJungling all game instead of raiding his own Jungle. This still leaves the ADC screwed if he leaves lane for far too long. Rule #4 of the Summoner's code, you never play at the expense of someone else. Unlike the Jungle camps however, we do have the timeline giving us a bit more context on when and the ADC died and other details. Details such as Jhin repeatedly dying alone and MF snowballing all hell Despite the fact that, normally, Jhin counters MF. Or, details such as the Tristana's early game being riddled with teammate contributions outside of just Singed.
I also implore you to do deeper research into his past, as there are episodes like this that occur, and many more...interesting, matches the farther into his timeline you go.
Admittedly I have less research than I would want for an "educated" opinion, but all the evidence I have found so far are either damning the Singed player or are chipping away at his argument's credibilities. Why, the other reply to my last comment mentions that he drops a whole paragraph on people in Champ select. In the vast majority of solo q situations, that just does not sound like a viable way of treating your teammates; you literally just dropped a brick (of text) on their heads. Or there are games where he does appear to steal the Jungler's farm. And there are games where it just seems to be that his ADC is dying alone, repeatedly, in the early game. The big picture just does not look like he's totally innocent, one way or another.
EDIT: It also would help if you read what I write towards Sworeclipse