Tom Welling’s reluctance to verify relationships stems from his time on Smallville . In early seasons, his private life was heavily scrutinized (regarding his marriage to Jamie White). Following their divorce in 2013, Welling adopted a "blackout" policy on his private life, rarely speaking about partners in interviews. This privacy is exactly why terms like "verified" are so hard to apply to his dating history—by design, he keeps it unverified.

There is another plausible explanation:

While there isn't always a strict follower requirement to begin the process, RouteNote suggests that reaching certain milestones often makes verification the logical next step in professionalizing a digital presence. The Road Ahead