I've seen people test that on allistic and autistic toddlers. Most (but not all) very small allistic children get separation anxiety if their caregivers leave them alone in an unfamiliar place, so they'll cry or seem visibly upset, but autistic children don't always react how allistic children do, so they might not cry or seem upset even if they do get anxiety, or may not get anxiety at all (which doesn't mean that they don't have an attachment to their caregivers, despite what people try to infer from that).
Even when I had an attachment to my sister as a toddler I don't think I cried that often, despite getting separation anxiety.