Delete a zero-diff quirk and update INDEX-related comments#70398

BruceForstall merged 2 commits intodotnet:maindotnet/runtime:mainfrom

SingleAccretion:Arr-Addr-Index-Delete-Quirk-UpstreamSingleAccretion/runtime:Arr-Addr-Index-Delete-Quirk-UpstreamCopy head branch name to clipboard