A sports photojournalist shoot people in action, unposed, unscripted, the PJ does not engage the subject and stays invisible, the key point is to tell a story, not create one. Pictures are a result of photographer's reaction to a scene or subject. He specialize in capturing actions and finding frames that tell stories and he also specialize in being unobrusive so as not to influence the behavior of the subjects.
A portrait photographer, especially one for a magazine or commercial advertiser, pose and direct the subjects, engages the subject into conversation and emotions, and injects a lot of influence to the subject. Pictures are a result of the subjects reaction to the photographer (note the differences). He specialize in portraying the human form in pleasing and artistic manner and he also specialize in communication and subject interaction, professional models or normal people who are uncomfortable with posing, he still gets the work done.
Put a portrait photographer to capture news and sports action, he is a fish out of the water, put a sports PJ to create beautiful portraits with a visionary statement to represent the country, this is the result.
Of course there are photographers that does both genres.
Also to newbies, they think its the same. Its not about photography basics of exposure or compositions bro, that is hobby level. Its about work.