There are two senses in which life's meaning might be subjective, though. It could be subjective in that it depends on us to invent it or to figure it out, or it could be subjective because its content is arbitrary, wholly imaginary, or even delusory.

I think you're talking about subjective meaning in the first sense, whereas the nihilist pushes for subjectivity in the second one. The cosmic perspective is supposed to demonstrate the second, more alarming kind of subjectivity about the content, not the construction of our worldviews.