We'll have to agree to disagree.
The language you quoted (from the CRL) assumes that the SPA is not in effect. The FDA has absolute authority to reinstate the SPA were it desirous of doing so (as a practical matter, who would challenge their doing so?). There is scientific evidence that has surfaced since the rescission that supports the view that there is a reasonable chance that lowering HTG (as opposed to lowering normal levels of TGs, which is all AIM HIGH, HPS2 THRIVE, and ACCORD showed) could have clinical benefit and which impeaches FDA's position that it is unlikely that reducing HTGs with Vascepa would have clinical benefit.
FDA could cite that evidence (if public justification were necessary, and I am unsure it would be) as the reason for its decision to reinstate the SPA.
FDA could also justify its reinstatement of the SPA (if it were necessary, and I doubt it would be beyond the above), by saying that it had not applied a proper guideline/procedure for SPA rescission (something Congress is interested in, as you know). In particular, in my opinion, to rescind the SPA, there is a reasonable chance a court would find that FDA would have to show that there is new evidence (arising after testing has begun) demonstrating either a public health problem or (here) that the premise underlying the surrogate endpoint is unlikely to be true.
It may be so that FDA has never withdrawn a CRL (I have no idea). I also don't know whether they have ever reinstated a rescinded SPA. I do know that FDA has never before had a court enjoin enforcement action for off-label promotion, and I believe they think such is very bad legal precedent that is not in the country's best interests. So to FDA, what would be the greater harm, reinstating an improvidently rescinded SPA and approving the sNDA for a drug that has a placebo-like safety profile, or making Amarin v. FDA established legal precedent?
From Amarin's standpoint, I believe Amarin would be getting much more under this scenario than they would be giving up. Nothing Amarin would be doing relative to the approved ANCHOR indication (and that would be a lot that could increase scripts and insurance coverage) would be "off-label" promotion. I would gladly give up the ability to make the DS claim in return for the ANCHOR label.