Ambiguous Vacatur in Lindke v. Freed

As Eugene has noted below, the Court issued its opinions today in two cases about the First Amendment status of the social media posts of government officials.

One technical but interesting note is the way that the Court ends its opinion in Lindke:

To the extent that this test differs from the one applied by the Sixth Circuit, we vacate its judgment and remand the case for further proceedings consistent with this opinion.

One thing that the Court commonly does when it announces a new test that might or might not be consistent with the lower court's opinion is to (1) vacate and (2) remand for proceedings consistent with the Supreme Court's opinion. This might well result in the original judgment being reinstated, but the judgment is vacated first, and then the lower court figures out what to do. But notice that the Court does not quite do that here—here it vacates the lower court's judgment only "to the extent that [the Court's] test differs from the one applied by the Sixth Circuit."

So what has been vacated? Is this a partial vacatur? That is, is the Court saying that the lower court's judgment is only partly vacated? It makes sense to partially vacate an opinion, but I am not sure how the Court could only partly vacate a judgment. The Sixth Circuit's judgment was the affirmance of a district court's grant of summary judgment to the defendant. If the Court envisions a partly-vacated-partly-affirmed-affirmance it might thrust us into the puzzle about exactly what a "judgment unit" is, as discussed here by Richard Re.

Or is this an ambiguous or conditional vacatur? That is, I take it the Supreme Court might be saying that it isn't sure whether the lower court's judgment needs to be vacated, because it isn't sure exactly what the Sixth Circuit's test is. (Or perhaps different justices who joined the unanimous majority read the Sixth Circuit's test differently, even as they all agree what the test should be.)

On this view when the Sixth Circuit gets the case back, they first need to make a threshhold judgment about whether their own judgment has been vacated, and then if the judgment has been vacated the panel needs to redo the analysis under the new test. I understand how this works, but it does have the funny feature of effectively delegating to the lower court the task of deciding what the mandate of the higher court has been. As a practical matter that may be perfectly straightforward, but as a formal matter it seems odd and not something I'd seen before. And in future cases ambiguous or conditional vacaturs could be much more interesting and even mischief-making.

Again, as a practical matter I'm sure this will work out straightforwardly on remand, but I wonder whether we will see more "To the extent that X, we vacate/reverse" decretal language in the future.