Note it could also be platform dependent. I'll give it a whirl on my own (new) machine.
Do you think that it may be caused by use of comptime? I have not looked at the benchmark implementations, but that kind of struck me as a reason
Well, I ran it again and now it's 10% slower than rust (the best rust impls have gotten better since I last tried); I think there's a simd optimization I'm missing, I'm not doing simd operations in the "pairs" phase