The calc case drew from single-element lists, so its pinned bytes were
constant wherever the rng sat — it could not have caught a change to how many
draws a calc consumes, which is exactly what the operand hold changed.
Multi-element lists make that stream a pinned fact, and every pinned pair
multiplies correctly, so the hold is pinned with it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>