This is pretty par for the course when it comes to a lot of edgy internet leftists. They've read a few essays on Marxists.org and think they know philosophy.

There's literally an entire body of philosophical work about the nature of epistemological truth, realism, naturalism, constructivism vs positivism and so on. Some subset of that surely intersects with economic philosophy, but the idea that this is a construct unique to capitalism just reeks of "I'm 14 and this is deep."