Nothing I look up supports your contention. I don't believe your claim.
The Supreme Court and all courts established by Act of Congress may from time to time prescribe rules for the conduct of their business. Such rules shall be consistent with Acts of Congress and rules of practice and procedure prescribed under section 2072 of this title.
I don't doubt that SCOTUS has a seniority practice that it follows, and maybe Congress did direct the order of releasing SCOTUS opinions. But "look it up" isn't a strong defense of your claim.
Just look at least year’s decisions: https://www.supremecourt.gov/opinions/slipopinion/20
Three decisions were released on July 1, 2021: the last was per curium (”by the court”) but with Kagan and Sotomayor dissenting, the 2nd to last was written by Alito, and the 3rd to last was written by Roberts, with separate concurrences and exceptions from the others in the majority, which is consistent w/ the below write-up on decisions release practices from UScourts.gov:
Opinions
All opinions of the Court are, typically, handed down by the last day of the Court’s term (the day in late June/early July when the Court recesses for the summer). With the exception of this deadline, there are no rules concerning when decisions must be released. Typically, decisions that are unanimous are released sooner than those that have concurring and dissenting opinions. While some unanimous decisions are handed down as early as December, some controversial opinions, even if heard in October, may not be handed down until the last day of the term