Could be that Watson wanted a shot the Houston and the NFL shortened it 1 game to give it to him. Maybe that is their punishment to the Texans.
I highly doubt that anybody involved cared about what Watson wants.
It's far more likely that the NFL just wanted to ensure that Watson accrued a season and the Browns didn't reap the benefit of having him for part of the year while still getting him all of next year on that first-year contract number.
I'd wager that they were locked in on either 11 games or a full season and nothing else was an option.