Question about Flexible Sync operators

In the Flexible Sync Permissions Guide, the Restricted News Feed use case uses the $in operator to allow permissions to any value in an array:

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But in what seems to me to be an analogous scenario in the Dynamic Collaboration use case, where I was expecting to also see the $in operator, it is not used:

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So I can better understand how this all works, can someone explain the distinction between the rule constructions of these two use cases? Thanks!

@Ian_Ward perhaps? :pray: