Constant SOBOL_POINTS 

pub const SOBOL_POINTS: u64 = _; // 4_294_967_296u64

How many distinct points the sequence has: 2^BITS.

The Gray-code evaluation only consults the low 32 bits of the index, so point 2^32 is point 0. That is a property of the construction, not a bug to fix by widening — but handing it out as a fresh low-discrepancy point would be, so the sampler stops at the budget instead.