Despite the slight differences in WAR, I'm still inclined to give the award to Correa.
Lindor has made himself one hell of a case, to be sure.
I still do value the success of the team in some respects, and the fact Correa has been their 3 hitter for the majority of the year and provided the impact he has is the only advantage IMO.
My issue with comparing team success, especially with mid season call ups, is that it doesn't always correlate to the individual players actual effects on the team record.
For example:
Indians record before Lindor: 28-33 (45.9%)
After Lindor: 40-37 (51.9%)
Astros record before Correa: 34-24 (58.6%)
After Correa: 42-40 (51.2%)
Twins before Sano: 41-37 (52.5%)
After Sano: 31-30 (50.8%)
So the only player who has made the team better on their arrival, going off of team success with that player on the actual team, is Lindor. Now, obviously there is more to it than that, but if team success matters, shouldn't this be considered?
And that goes back to this belief I have, which may be biased...there is no correlation between the Astros playing well because Correa is playing well, or the Twins playing well because Sano is playing well this year...but it is pretty apparent that the Indians are playing better because Lindor is playing better.