The NFL will reportedly be more inclined to call false starts this season after Atlanta Falcons owner and member of the league's competition committee Rich McKay said the "Petyon Manning rule" has not been emphasized in recent years, according to the Atlanta Journal-Constitution:
“This wasn’t a rule change, this was a point of emphasis this year,” McKay said. “[Simulating a snap] could include a tight end, a running back and, in this case, the point of emphasis was on quarterbacks and their use of thrusting their hands and making quick and sudden movements.
McKay said that a quarterback is not allowed to simulate a play or have any sudden movement at the line of scrimmage, and that it's at the replacement ref's discretion to decide when those movements warrant a penalty. He also said that certain quarterbacks, including the New Orleans Saints' Drew Brees and the Falcons' Matt Ryan, would likely be affected by this point of emphasis because of their style of play.
The league took a lax approach to the rule in recent years as a way to let teams communicate in so-called "hostile environments." But the NFL notified the NFLPA in March that it would be cracking down on those who exploit the rule, and it was communicated again to the players through written statements and footage during training camp:
“We were very focused as a league in allowing quarterbacks to execute the silent count,” McKay said. “What you saw people doing was raising their leg once, then raising their leg twice, and ways to communicate so defenses couldn’t just tee off on the offense. But what happened, you started seeing quarterbacks move their hands forward, and a lot of different things that we sudden movements that were not allowed under our rules.”