Normally I wouldn’t care, since both are very similar things, but if solo (side) project is set as “Person”, date attribute is automatically changed from “Began” to “Born”.
For example, persons name is William Malon, he is born in 1977 and he has side project called Void, which is started in 2010. So, if I want to enter data correctly, his side project type must be changed to “Other” or else project “Began” date will appear as “Born” instead.
According to some users who downvote my edits, there is no distinction between person and solo (side) project and both must be set as “Born”, thus making entry entirely incorrect. Seems like an oversight to me.