When I look at previous year's Olin thread, the interview calls were out at the beginning of October itself. Even the first admit announced himself/herself on the 10th of October. I guess, by this time last year, the adcom of Olin must have been done with R1.
There can only be two explanations to 2015's anomaly :
1. They have undergone a drastic change in the way decisions are taken and selection done. May be, because they have such a minimalistic app, they have decided to do selections directly without interviews and will announce the decisions close to the decision date.
2. They have read all the trolling done on the GMATClub and have decided to take revenge and not invite any GMATClub member to interview except for the ones already invited at the very start. In this case, Olin stands to loose out because the average of GMATClub members is much higher in every parameter compared to the school's average.