It’s not that dWAR has to confirm pre-existing beliefs. Like most stats in baseball, it’s just difficult when comparing players whose careers started so far apart.
The baseline for a lot advanced metrics on both sides of the ball is the league average. In this case, people are taking numbers compared to league average center fielders from the 70s and 80s and comparing them to numbers based on center fielders from the 2010s. It’s actually a big deal. MLB has gone through periods where defense was valued differently by varying managers and GMs, which is why players like Tony Armas and Alfonso Soriano have played CF.
Lynn did have some stellar defensive contemporaries, like (the tail end of the career of) Paul Blair, Rick Manning, Andre Dawson and Cesar Geronimo. But also a lot of Chet Lemon/Gorman Thomas types who would be corner OFs today, but played CF because they could hit and played for teams that valued the offense.
Bradley has a lot of stellar defensive contemporaries as well, because the focus on defensive metrics has created a league with more players playing CF who might have been relegated to reserve duty in the 1980s, like Kiermaier and Pillar...