That is actually wrong. A strobed photo almost never looks literally natural. A single light setup can get close, but the falloff is still wrong without some pretty careful post work.
With a light touch the average viewer will accept it as naturalistic. We're so used to multiple lights that we don't notice gently applied fill and it reads as natural. So in some sense it looks natural. But not a literal sense.
Sometimes you can sell your fill as a naturally occurring reflection, perhaps.
It's not, though, generally all that natural looking. What it is, is compliant with contemporary standards of photographic lighting. Which change constantly.
Ideas of what looks natural and proper in photos are local to venue and time. Cross an ocean, wait ten years, and all those immutable undeniable basic truths, those objective realities, will all be wrong.
Not sure how you're supposed to fill when you're using a 300 to shoot a speaker who's talking right now, and could wrap up at literally any moment. You're gonna need some really long arms, a psychic assistant, or super-speed.