Nope, it is only a guideline

"Are you completely safe after waiting 60 days to attempt to change your status? No. Notice that the FAM also mentions that immigration officials can act on facts giving them a “reasonable belief” that someone misrepresented his or her intent. In a marriage-based case, for example, it would be all too easy to get caught in the lie during the process of proving the bona fides of one’s marriage"

http://www.nolo.com/legal-encyclopedia/will-3060-day-rule-help-clear-suspicion-about-your-intentions-upon-us-entry.html