With a mod that allows age manipulation (character reload) I tweaked around, and it seems that characters between age 21.00 and 21.99 use teenager portraits, but adult character models, so encyclopedia will show them with facial hair, but portraits in town menu will show them without. Before 21.00, they use teen model on the map and encyclopedia, when they turn 22.00 they use both adult model and portrait. I saw this happen to characters on a game untouched by any mod, only using the ctrl+c command in character creation to change the age of my character during campagain setup, but this allowed to pinpoint the issue.