how does approval voting allow for spoilers? The experts that study election systems consider it eliminated under approval voting. It’s literally impossible to be a spoiler, because there’s nothing to spoil.

I suspect he’s thinking of it’s tendency to trend towards moderates. Like say 60% strongly prefer A, 30% strongly prefer C, but many supporters for either would also be OK with B. Under a lot of ranked choice and similar systems, B has no chance and A definitely wins but under approval if enough A and C voters also tick the box for B then B will win, even if B was only the top choice for a tiny minority because they were “good enough” for enough people.