I'm okay with the water that blueberries actually CONTAIN, and the same with any air INSIDE them.

I just don't think that "air that had separated each berry from its neighbors" should count.

> Supposing that the entire Earth was instantaneously replaced with an equal volume of closely packed, but uncompressed blueberries, what would happen from the perspective of a person on the surface?

Closely packed but uncompressed means you're going to have air between some bits of them.

More importantly, that description means Earth's atmosphere is left behind.

Or sonething else, like Methane. If we put vacuum sealed blueberries on the moon, they wouldn’t be separated by air.

No, it doesnt mean that.