It doesn’t mean that Johnson or any other player affected by the provision will definitely show up by August 10, the last day for players under contract to report in order to earn a year of credit toward free agency. Though the teams possibly believe that they hold the cards, the reality is that, while a year of credit toward free agency moves a player closer to the open market, the player can still withhold services from his current team, if he’s wiling to pay the daily fine, to possibly give back some of his signing bonus (if any), and ultimately to sacrifice game checks.
For guys like Johnson and Revis, the thinking is that they’ll get new deals before they ever become unrestricted free agents. So the question isn’t whether they’ll give up a year of credit toward something they’ll likely never be, but whether the teams are willing to go forward without them during training camp, the preseason, and possibly a portion of the regular season.
This doesn’t mean that they’ll definitely hold out. But it does mean that, as applied to truly elite players, the 30-day rule doesn’t have quite the same oomph, especially when applied to a guy like Johnson, who is still three years away from free agency.