I don't think it's a watershed moment in Church history.
That's to be expected after having been poisoned by some of the false principles of R&R. For you it matters nothing what a Pope commands and teaches; you just do what want anyway. So for you this means something, when it should mean a lot to someone with a true
sensus Catholicus.
This forces R&R to simply reject the Disciplinary Infallibility of the Church in principle, because the argument that it was never made mandatory has just been completely scuttled.