That Google feels the need to retire Octane over this is almost unbelievable... there must be some ulterior motivation.
Why that assumption? Google explained its reasons quite clearly:
Google is retiring the benchmark suite so that good-intentioned open source developers will not be able to use it as a proof point for why their patches improve performance, when in fact they don't.
P.S. It seems one other group is disappointed that the benchmark is going away, though, and that's Chromebook fans. They've been using Octane to benchmark the performance of hardware from different vendors running the same version of Chrome OS. That still seems like a legit use case to me.