There is no simple answer to this. The Biography or TImeline should certainly include facts that do not fit the birth, death, marriage, children, etc. data at the top of the Profile. Occupations, places lived, military history, wills and probate, surrounding historical events, etc. It does not always need to repeat the facts above, but since there is no way to add sources to the facts above,they need to be repeated if we are to give specific sources for specific facts - a desirable approach whenever it is possible.
In a lot of cases, all we know is the most basic facts. In those cases, the short Bio may be the full story. But even then, if you know from a study of local history that the basic events occurred at the time a community was first settled, or it was disrupted by events like King Phillip's war, adding this information can certainly make a Profile richer. A Timeline that includes such historical events is an excellent format, but it takes a lot more work and study to do it well.
I'm not sure how you see using the Timeline approach. It doesn't fit all cases, Suppose you know the names of 10 children, because they appeared in a will, but you have no birth date information. I don't think this fits a timeline, but it belongs in the Bio narrative and sources.
Your question is an excellent one, and needs to keep being discussed. Your concern for best practices is very welcome.