There is no reason they can't just enter the == Sources == without the inline code. I do it all the time to add census records, FindAGrave and other data sources. I don't particularly enjoy writing bios because I am usually adding sources to non-family members that I don't know. I do add == Sources ==, however, because they are required by the Honor Code.
It is pretty easy to add an inline if you want. In the bio section, click the little C for Citation button and paste your citation between the inserted codes. It really couldn't be easier. Just make sure the Sources section has the <references/> line:
== Sources ==
Just copy and paste it from the right side of the screen under the Biography section. The inline sources will appear above the <references/> and any other sources should go below the <references/>.