Strange Pluto performance on Binder

I created a Pluto notebook to capture some the performance tips in the manual, and everything seems to run fine on my home computer. But I am getting an odd result when trying to run the notebook on Binder using this Pluto-on-binder link.

Specifically, I copied the @simd example from the Performance Annotations section, which is

@noinline function inner(x, y)
    s = zero(eltype(x))
    for i = eachindex(x)
        @inbounds s += x[i]*y[i]
    end
    return s
end

@noinline function innersimd(x, y)
    s = zero(eltype(x))
    @simd for i = eachindex(x)
        @inbounds s += x[i] * y[i]
    end
    return s
end

and it runs fine where innersimd runs roughly 8x faster than inner on my home computer’s 8 threads.

However, when I run the notebook on Binder, the two functions are nearly identical in runtime. Threads.nthreads() shows that I should have four threads available in the notebook, so I don’t understand why I am not seeing the @simd performance boost. What am I missing here?