Ive actually found that even when adding fruit, a secondary is not necessary unless you dont have enough head space. I usually just wait about 4 days until the bulk of fermentation is complete then dump the fruit directly in my primary.
I've wondered about that.
I did a side by side with a generic wheat beer with Peaches. Secondary one batch, primary fruit with other. The primary tasted better, i picked up a hint of oxidation on the secondaried batch. If you've got the headspace it works. Its no different than adding honey or candi syrup or sugar syrup to the primary after the bulk of fermenation has completed. FWIW I also dry hopped both of those beers. So the one went something like this.
Ferment for 4 days
Add peaches to primary after 4 days, and ferment for one week.
After a week add dry hops and ferment another week, all in the same primary. Worked great!