Please get your facts straight on this. The U.S. Senate is NOT in recess.
You are right. The President used the Vacancy Reform Act which gives him 210 days before confirmation. Nothing illegal about it.
That's why the complaints about the appointment have been so muted -- and they've come almost entirely from lawyers and think-tank types outside of government.
What's Chuck Schumer or Nancy Pelosi going to do -- complain about a vacancy appointment that's been done under an unconstitutional law that they both voted for in 1998? LOL.