if you post a public message, someone can ingest that message. there's no protection in what you're citing
(for the record, no such protection on public mastodon messages either)
you're claiming a protection that does not exist
bluesky is a capitalist endeavour funded by cryptobros, while mastodon is not. bluesky has a financial incentive to do quiet seedy things behind the scenes with your data mastodon does not. any secrecy like elena cites is a warning you should heed