Deference only applies where the law is not specific.
But it only applies to to laws. Unless I misunderstand what you mean by "policies", it shouldn't apply there. Since it sounds like you're worried about overreach due to application of chevron deference, I was trying to see if I followed your train of thought correctly.
In my extremely limited understanding, the issue with the RIFO and Chevron Deference is that the gap is so damned wide with regards to how to regulate the internet that there needs to be a better test than "does the solution proposed in the RIFO fill the gap?" I would consider the RIFO to be such an outlier in cases of chevron deference law that it almost looks like a strawman when compared to other uses of chevron deference. We should definitely shore something up to allow future questioning of the wisdom of courses of action recommended by agencies when consulted in deference matters once the consequences of such deference have come to fruition, but that very possibility (as I understand it) is part of WHY the deference to agencies occurs instead of simply allowing judges to decide. The people at the agencies, being theoretically put in power for a set term, have more to lose from bad decision-making than judges-for-life do.