given very little details (as you pointed out) my main concern is in qualifying what he meant by 90% in terms of the 'trajectory' of recovery.
-If he has steadily improved since surgery and continues to inch forward (he is better now than a month ago, week ago etc.) ....my guess is he is fine to play.
-If he, at some point prior, was 'better' and has dropped back to 'only' being 90% that would be much more of a concern to me.
Hard to say anything concrete for obvious reasons but my suspicion is the former. If he had taken a step back in recovery, the team would/should exercise caution.
To echo what the captain said....groin injuries can be a nightmare. It's hard to accelerate, cut, push off tacklers etc. with that type of injury...and they can be very stubborn to heal. I'm sure he has been cleared medically and it is just a matter of how he feels. At present, he's 90%. Could all just be Stevie playing a little mind games with Mr. Island as well.