So we disagree. IMO as previously stated: more screen real estate (in this case 16" versus 14") does substantially improve productivity for many workflows. No one said it would "make or break anything," just that it substantially improves productivity. That observation is based on using Mac laptops since the Duos in all kinds of scenarios with multiple different types of apps.
External displays indeed are useful of course when a MBP is in desktop mode, and I use three. The same logic applies to mobile usage. You could do the math, but 16" does provide substantially more display real estate than 14" does. Note that I do not say folks should not buy 14", just that they should realize that there can be a productivity loss for those doing substantive work (as opposed to primarily content consumption and email) on a mobile box.
Sorry but I do not understand your suggestion that people who perceive productivity improvement may "have other issues." What other issues?