That's not in the article. And the IRS website contradicts it. You may recall somebody on ET a few years ago described falling afoul of this law (FBAR rather than FATCA, but the penalties are similar) after following advice from a consultant - legal interpretation of "willful" may not be the same as common sense - despite having declared and paid tax on all his income.

retrospective as it should be

Why "should be"? What's wrong with being able to challenge laws for being unconstitutional without being harmed by them, as in Germany? There are arguments both ways. Contrary to what some Americans think, "is done by the US" is not the same "should be"

plaintiff must have suffered an actual, factual, and material injury, or "loss"

Are you implying that the lawyers were so ignorant as not to know that? The debate was specifically about the meaning of "suffered"

A foreign bank's refusal to accept U.S. clients may be related to FATCA's reporting requirements, but it is the bank's decision and that injury cannot be imputed to the U.S. government, the panel ruled.