I agree that some of the larger-seeded beans can be less productive - to a point. I did get nearly 4 pounds of seed from "Jembo Polish" in 2021, from a 16-foot row. Might have had close to that from "Bird Egg #3" this year, had I planted on time. To put that in context, the larger-seeded beans tend to have fewer pods per plant, so they might not be the best choice for use as snaps regardless of their flavor (and both "Jembo Polish" and "Bird Egg #3" have excellent flavor). But for shellies - which is their best use - the productivity is decent.
One large-seeded pole bean which goes by several names ("Ma Williams" / "Goose" / "Pumpkin Bean") manages to be an exception to the rule, in that it is highly productive as either snap or shelly. The snaps are unremarkable, but heavy pod set makes it OUTSTANDING when let go for shellies. I had over 4 1/2 pounds of dry seed from "Ma Williams" when I last grew it in 2016. It was supposed to be grown for renewal this year, but was one of the unfortunate cancellations.
View attachment 52962"Ma Williams" 2009 shelly harvest