The expert was telling the audience of fundraisers that they should not tell the most exciting stories about their work, but their most "average" stories. Reason: the exciting stories are "outliers" -- not real representations of what you do.
And ... well ... donors don't respond to outliers? He never quite made it clear what the downside of the exciting stories really is, other than that they're less common than the average stories.
That expert has never had to raise a dollar for charity.
If he had, he wouldn't be giving such terrible advice. Advice that makes complete sense in the world of his area of expertise. But it's destructive balderdash in the world of fundraising.
Advice from experts who don't know what it takes to raise funds is a real impediment in our industry, as noted by npEngage at Cutting Through the Noise -- A Fundraiser's Strategy for Sorting It Out:
... before you change your strategy because of something you read or watch online, ask about the credentials of the "advisor." Are they talking from the perspective of having worked passionately to raise money -- and learned something in the process that was worth sharing? Or are they just talking theoretically about what would work in a world in which our donors actually started behaving like the "experts" say they should?
I've had my share of theories that looked good on paper but didn't stand up to the real world of asking real donors to give real money. I hope I'll never start pushing my theories before they've been vetted by the Real World. Unfortunately, there's no shortage of experts selling ideas that haven't been field-tested.
There's nothing wrong with trying something new. That's how you innovate. But you should know it's new, that it's untried, and that the chances of failure are high. That way, you can limit the risk and fail smart. Or succeed even smarter.