Underwriting is only as honest as the numbers underneath it. Most pro formas are built on quotes: a bid from a stranger, a price from a catalog, a schedule from an optimist. Quotes are what the market tells you. Lived numbers are what the work actually costs.
The difference decides which deals exist. Run feasibility on market bids and a thin deal dies on paper. Run the same deal on lived numbers, on what material costs landed at wholesale, on what labor costs when the tradesmen quoting you are the same men who buy their material from you, on what a schedule really does because you've run the site yourself, and some of those dead deals stand up and walk.
That's the honest meaning of "deals pencil here that don't pencil anywhere else." It isn't magic and it isn't appetite for risk. It's just better inputs. The margin other buyers need as protection against numbers they can't trust becomes margin the project keeps.
It cuts the other way too, and this part matters more. Lived numbers kill deals that quoted numbers would have blessed. A pro forma built on somebody's brochure will happily walk you into a loss. Real costs have said no here more times than they've said yes, and every no was cheaper than the yes would have been.