If it passes the House, it doesn't matter, Trump can veto it.
Immigration and Naturalization Service v. Chadha in 1983 declared Legislative Veto unconstitutional. It should have been then when all the emergency powers were rewritten.
So as it stands. All those emergency powers that were written with the understanding that a simple majority was all that was needed to end an emergency, now need a veto proof majority.
You're mostly right in that the person you're replying is missing that we are providing money for those people's detention. But El Salvador doesn't HAVE TO give the person back, there's nothing outside of us stopping payments that compels them.
It's a semantic difference indeed but goes to point out the difference between legal means and diplomatic means. Legally, there's nothing the US can do, once the person is in El Salvador they are under that country's legal system. Diplomatically, yes, absolutely we can ask El Salvador to hand the person back or there will be diplomatic and potentially economic consequences for not doing so.
Now as others have pointed out, the Executive branch has a wide latitude for diplomatic powers. Judge indicated that the President work diplomatically to bring the person home, but outside of that, the "or else" part. There's not much the Judge can do past that.
Additionally, El Salvador could press charges on the person and then there would be nothing that can be done to bring the person home in any legal means and likely less so diplomatically. This is the issue with sending people there. President Bukele of El Salvador could wish for better diplomatic relationships with the United States and Trump and just invent charges to keep the person there forever. There's literally nothing we can do is El Salvador indicates that they are keeping the person and there's nothing in the court system that can compel anyone to make those reasons clear.
That's the biggest thing about the difference between diplomatic and legal. In legal means, the Court system can ensure that people are following through on requirements. In a diplomatic means, it's just depends on who can butter who's biscuit the best. The Judge can tell the President to bring him back, but that means next to nothing when it comes to diplomatic matters.