It would be a big mistake for the Browns not to play their starters during preseason for this reason.
They need to develop game consistency with all the new players they have brought in.
If they do not play these players in all preseason games, that means that the first 6 or 7 games of the season will be their preseason. This is a no no. They need to hit the ground running to compete in the NFL The first games are against divisional opponents. Surprise! Sorry, not sorry. Must be already in mid season form because they will be.
Why rest players who have been resting all off season? Time to get tough and season ready.
You've got new players, new coaches, and new schemes. A country club atmosphere is not needed and would be a big mistake.