Just because the observable world is testable doesn't mean that subjectivity doesn't hold any value.
But this philosopher's claim isn't subjective. It's not "hey I think it would be cool if all matter were conscious." It's a pseudo-factual claim about consciousness. It's not subjective at all. It's just neither wrong nor right. It would be like me claiming that there exists a being called "god" who has never and will never interact with this universe in any way. You can't predict anything based on this pseudo-factual claim, which means (IMO) it has no real truth value. On the other hand, it's definitely not a "subjective" viewpoint as most people conceive of subjectivity.
But in turn I can say everything you know and experience about the world is subjective. It came through your senses and you have no way to know if it was the same with other people.
For example, playing a video game, there is some kind of objective physical activity occurring in reality. Subjectively, you perceive a cartoon world with Mario bouncing around on koopas. If the CPU has its own subjective experience of the very same objective physical phenomena, it probably doesn't involve the perception of Mario and koopas.
I think there is probably tremendous value in figuring out what it is about the universe that enables these different subjective experiences, when and how they arise, how they're similar and different, etc.