I know a number of lawyers and they would disagree with that assessment. If the Supreme Court refuses to grant a writ of Certiorari it is generally because they do not believe the lower court decision needs review. In a constitutional case, like Quirelli v. Morton Grove, you had the first instance where a municipality outlawed the ownership of firearms. Yet the Supreme Court refused to hear the case but instead let the lower court ruling stand. The reaon is that they saw nothing in the lower court ruling that needed review.
Do they then agree with 95% plus of lower court decisions?
It seems unlikely to me. There are many reasons why they might deny cert, such as simply believing that the case is not “ripe” or that the issues are not clear enough, or issues that they are not willing to address.