Not all, or even most, games are made by billion dollar studios. Overlapping roles are still the norm in small studios. And even those that do have bespoke designer roles would likely benefit from telling them that computers have certain limitations where trade-offs in game design need to be selected for, because many AAA games run like shit. Many times for reasons other than the game design, sure, but also sometimes because of ways that could be worked around more easily if the game design were accomodating the tradeoffs.