True, but if Meta (or anyone) wanted to “directly” get that data, it would be as trivial as setting up an instance on something as small as a Raspberry Pi and subscribing to a community here. We would have no way of knowing who it is or stopping them. Defederation is a tool to prevent brigading, not lurking.
If (if) Meta wanted to set a lemmy-style platform, preemptively defederating from it would be a largely symbolic gesture. Doesn’t mean it’s not worth doing, like I said we’ll cross that bridge if and when it becomes relevant.
The downvotes are all coming from accounts on other instances, which as @ValueSubtracted@startrek.website suggested, makes us think it’s most likely people browsing “All” and not appreciating seeing twenty discussion posts (not that that justifies it).