We appreciate your situation here Nolan and share your concern. The start to this race was a bit hectic, with me scrambling to get the tracker started properly (after forgetting to add a team until the field started rolling). I finally got it going about 5s before I gave the field the green, and the 5s gap was of course used to bring up the menu to throw the green.
Thus I didn't see the accident going on, and neither did Benji as he was driving the SC. Once I gave the green I switched to watch the leaders go through T1 (watching for trouble) and it wasn't until they were on the way to the lefthand sweeper that I heard Benji say "looks like there was some trouble in the back." By this time it was more difficult to estimate how big the wreck had been, since everyone was already moving again.
Obviously these weren't ideal circumstances, but we should have had someone notice the trouble sooner. At that point we had only myself, Benji, Burnsy, and Starblue (who was also working on the tracker at that point). Rooble joined later.
Now... as to whether the accident should have brought out the SC:
The rule on the books says that one criteria for a SC coming out is that "a portion of the track is badly obstructed or an incident involves a majority of teams." I have not done an exact count, but I gather this incident included 5-7 teams out of 28. For comparison, the restart incident at BL1 included literally half of the field or more, which is why it brought out the SC and why it's the only non-flipping/non-fuel/non-stranded related SC that's been thrown. So on that criteria this incident would not have counted.
That said, since it happened before the green, we would ideally have aborted the start and taken another lap at SC speed. However, as you pointed out, there was only a 2s gap between the incident and the green flag being given, which is not much time to react and delay the green.
In short, in a perfect world the start would have been waved off, but circumstances conspired to prevent that. Hopefully circumstances will be kinder in the future.