It doesn't matter...it's not his first year in NBA he is not a rookie.
'Has anyone even bothered to look up the definition of rookie in the dictionary?
NBA eligibility rules make Simmons a rookie and eligible for the ROY just like Blake Griffin was.
"The dictionary" has no bearing on eligibility rules on any actual sport.
Even so, the Merriam-Webster definition of rookie is: a first-year participant in a major professional sport. There is no mention of contract but it does refer to being a participant. It is hard to be considered a participant when you are injured for the full season.
It doesn't say participating in games, it just says participant. You can participate in other team related activities such as video sessions, rehabilitation, training, ect..
We do seem to agree that no league should be bound by a dictionary. They're free to make up whatever rules they wish.
Common sense says if you are on a team and accrue a year of service that was your rookie year. I've always felt leagues that give players a do-over for a failed rookie year are making the wrong decision.
Others obviously see it differently, and I think they're wrong. But being that the rules are what they are, I'm not going to complain if someone wins an award based on the rules as they are.