Person a is an "older" baal teshuva (30-40 years plus) and grew up knowing he was a kohen. Being a kohen means that at his age there are not likely to be any baalas teshuva women he can marry and marrying someone who comes from a known "frum" family is often an obstacle and not prefered. Is it better this person look for a reason not to be a kohen such as being declared a chalal or should he just wait patiently and hope that one day he might find someone to marry?
BT's born after 1975 or so are almost guaranteed to be chalalim rather than kohainim. CYLOR for the details, of course, but there probably fewer than 1,000 true kohainim from non-observant families in the entire US below the age of 50. It's not a copout or a loophole to have yourself paskened a chalal, it's an acknowledgement of your actual yichus