Is he better off getting the information in another format the college will recognize?
This is the quintessential question. Some may say that while striving to maximize credits for credentialed formal education, it may be important to also give a nod to the benefits of life-long learning of the kind which may not earn credits/credentials.
Keeping a list or portfolio of learning experiences beyond those which may be required for a given credential may prove helpful when applying for educational, experiential, or employment opportunities as it may tend to indicate an interest and drive which go "above and beyond" requirements.
There are many individuals with a body of expertise developed outside of the formal education system. Such knowledge may be inspired by a pivotal life experience and can be a sign of strong internal motivation and personal dedication.
The thought of taking a formal course for credit in an area one has previously studied may call to mind the boring repetition and stagnation some may have experienced in elementary/middle/high school, however many college-level courses incorporate the lived experiences of the course professor alongside the text material and can therefore be very interesting and not seem like "repeating" a course. Additionally, there are new developments in STEM fields which both add relevance to each course taken, and also help manage student expectations regarding the need for ongoing professional development throughout their careers.
