Stats just don't bear that out.
In 5 playoff seasons with Dallas, Finley averaged 41 minutes, 18 points, shot 42%, averaged 5 rebounds, and 3 assists.
During the saem 5 regular seasons, Finley averaged 39 minutes, 19 points, shot 44%, averaged 5 rebounds and 3 assists.
That is about as close as you can get comparing the two. If anything, stats come down a little in the playoffs because most teams play a little better defense. He just got blamed for Dallas failure because he was one of their studs.