It doesn't take 7 Justices to change the balance of the vote. It does not require a unanimous decision.
In this case, a change of a single judge would have left the 5th U.S. Circuit Court of Appeals previous ruling intact.
Say what?
This was a 5-3 USSC decision and only 1 Justice found the Texas Statute Constitutional.
If you read the case you will see that only Thomas would uphold the statute as Constitutional, 5 Justices find the Statute Unconstitutional on its face and the other 2 Justices would remand to the trial Court for further findings of fact. Again only 1 Justice would find the statute Constitutional on its face.
It's becoming clear, to me at least, that the only way to undo Roe is through a Constitutional Amendment...