Men can be teenagers until well into their twenties. That is well known
The quote suggests that young men often carry the traits and behaviors associated with adolescence even as they enter their twenties. This stereotype implies a sort of prolonged youthfulness, where responsibilities and maturity might not be fully embraced. Such a notion highlights societal expectations and the way they can influence individual development.
In the context of Alexander McCall Smith's "The Handsome Man's Deluxe Café," this observation could reflect the characters and their interactions, possibly emphasizing themes of growth, identity, and the challenges of transitioning into adulthood. It serves as a commentary on the dynamics of maturity and the gradual journey toward becoming a fully realized adult.