Final answer:
Landon is seen as finally growing up by Eric because of his realization and action towards returning to his studies and setting a positive example for his daughter, reflecting personal maturity.
Step-by-step explanation:
Eric told Landon that he was finally growing up because Landon exhibited a mature understanding of responsibilities and the ethos of setting a good example, particularly in the context of family obligations. Through the narrated experiences, Landon learns the value of perseverance and the significance of being a role model, especially in the eyes of his daughter. This realization is a key milestone in personal development and maturity, which is why Landon's acknowledgment of his own need to resume his studies and not use his daughter's illness as an excuse represents his growth. Landon's decision to re-enroll demonstrates a renewed commitment to his own goals and duties as an adult which, in Eric's view, signifies that Landon is finally growing up.