[rocqua]

How does a twist x{d} being even equate to the integer d being even?

[throwaway080383]

The twist x{d} is even as soon as d>0.

[rocqua]

Yes, but that doesn't mean the integer d is even.

[throwaway080383]

I never say anything about d being even. Rather, as soon as d > 0, x{d} is even, so "almost all" x{d} are even. As you vary x and d, you cover all integers exactly once, so from this perspective, "almost all" integers are even.

My point is that this is very similar to how elliptic curves are being counted here.