Maybe they meant it's not a threat because people don't care about who they are following being revealed, since it used to be publicized on Twitter.

Though note that Twitter has a "list" feature that allows users to differentiate people they follow versus contents that they want to read[1], whereas Fediverse's "list" feature is more of a filter since users must follow an account first before it can be placed on a list[2]. I think the workaround for Mastodon would be to bookmark profile pages for people you want to check on but don't want to follow.

[1] https://lee-phillips.org/howtotwitter/

[2] https://docs.joinmastodon.org/methods/lists/#accounts-add

Honestly I think it is pretty realistic. The content is public, what about this would be particularly difficult?