Why would you assume they disabled SSE? Compilers generate SSE by default when optimizing, I would be very surprised if Peter Bright disabled it. And not only do normal C/C++ compilers generate SSE, but JS engines generate SSE as well. So SSE was being used on both sides of the comparisons here, I am pretty sure.

What was disabled was C/C++ code that explicitly used SIMD intrinsics or explicitly used SSE function calls in C/C++.