The antibody assays are not helpful, at a person level,
among other things high false positive/false negative rates as well as being confounded by multiple strains due to rapid mutation of the SSRNA genome
See? There's somebody who knows what they are talking about. Everybody knows about SSRNA genome. Multiple strains and rapid mutations are definitely confounding factors in trying to understand something. So just stop asking silly questions because somebody has already thought of an answer of why your questions are just silly.