I really think you need to be even more specific about where the opinion (which does have horrible reasoning to get to where it does go) ends up.

It not only does not hold that the President's extra-statutory program was valid, it doesn't actually hold that the PAA is constitutional on its face.

Instead, it does something even more limited - it reviews whether or not what the Petitioner was asked to do, specifically, violated the constitution. IOW, the court limited its ruling to an "as applied" as opposed to a "facial" ruling.

Let's say there was a statute passed that gave a police officer the right to pull over and ticket a driver for driving over 55 and also gave the officer the right to require that the driver allow a strip search in the middle of the highway. Someone who is pulled over for driving over 55 and ticketed, but not strip searched in the middle of the highway, files a defense to their ticket based on Constitutional claims about the statute.

In an "as applied" setting, the court would look at the pull over and ticket but not the strip search element; in a facial holding the court would look at the overall statute. So a court holding that someone could validly be pulled over and ticketed under the statute in an "as applied" ruling is NOT the same as a determination that the statute is constitutional.

From the ruling:

As a threshold matter, the petitioner asserts that its Fourth Amendment arguments add up to a facial challenge to the PAA. The government contests this characterization, asserting that the petitioner presents only an as-applied challenge. We agree with the government.
…
Here, however, thereis a particularized record and the statute –the PAA – has been applied to the petitioner in a specific setting. The petitioner’s plaints take account of this setting. So viewed, they go past the question of whether the PAA is valid on its face – a question that would be answered by deciding whether any application of the statute passed constitutional muster … and ask instead whether this specific application offends the Constitution.
...
We therefore deem the petitioner’s challenge an as-applied challenge and limit our analysis accordingly. The means that, to succeed, the petitioner must prove more than a theoretical risk that the PAA could on certain facts yield unconstitutional applications. Instead, it must persuade us that the PAA is unconstitutional as implemented here.

The court then goes on to say that it can trust that Gov isn't doing unconstitutional things with the surveillance and info bc, after all, the Exec is trustworthy bc it has good intentions - doesn't really need a check or a balance.

As opposed to, oh, say the reasoning in Katz (a Sup Ct case on intel surveillance of Americans on American soil) In Katz, Gov argued how reasonable they were vis a vis a warrantless wiretap and the Court agreed they were very reasonable.

"Accepting this account of the Government's actions as accurate, it is clear that this surveillance was so narrowly circumscribed that a duly authorized magistrate, properly notified of the need for such investigation, specifically informed of the basis on which it was to proceed, and clearly apprised of the precise intrusion it would entail, could constitutionally have authorized, with appropriate safeguards, the very limited search and seizure that the Government asserts in fact took place. "

But unlike the wiretapping decision by the kindasorta appellate court, the Sup Ct didn't go along with a "ah, why do the boys need a warrant when they're such nice young men and they voluntarily behave so nicely too" argument to avoid the constitutional warrant requirement.

Instead the court went on:

The Government urges that, because its agents ... did no more here than they might properly have done with prior judicial sanction, we should retroactively validate their conduct. That we cannot do. It is apparent that the agents in this case acted with restraint. Yet the inescapable fact is that this restraint was imposed by the agents themselves, not by a judicial officer. They were not required, before commencing the search, to present their estimate of probable cause for detached scrutiny by a neutral magistrate. They were not compelled, during the conduct of the search itself, to observe precise limits established in advance by a specific court order. Nor were they directed, after the search had been completed, to notify the authorizing magistrate in detail of all that had been seized. In the absence of such safeguards, this Court has never sustained a search upon the sole ground that officers reasonably expected to find evidence of a particular crime and voluntarily confined their activities to the least intrusive U.S. means consistent with that end

Take that next step here, that these are seizures of American communications where the Executive does not reasonably expect to find evidence of a crime, but is allowed to fish for that kind of evidence as long as they claim any "significant" foreign intel reason for the search, and you have to wonder why there is now even less protection offered up.