Sage, you've got this one backwards. There is zero question that running requires more fuel than cycling at similar relative intensity. This has been known for as long as we've been measuring oxygen consumption in labs.
If you've used the Stryd footpod, your power zones while running are probably 50 watts or more above your comparable cycling zones. (Not looking to start a debate about the validity of "running power," but what Stryd is doing is basically estimating metabolic power, then scaling it to cycling power measured at the crank. So if your Stryd "power" is 15% higher than your cycling power, you are burning 15% more calories.)
Now, if you put a pro cyclist on a treadmill and hook him up to a metabolic cart, it's possible he'll struggle to put up the same numbers, but that's just because he doesn't have any experience running.
OP, I think the impact of the carb craze on running shows up mostly in two places. First is ultrarunning, where the calorie needs are extreme and having more carbs allows one to operate at a higher relative intensity. Second is in training. More athletes are aware that lack of adequate glycogen is interfering with quality workouts, and there's more attention to ensuring that they enter those key sessions with sufficient fuel.
I don't think the carb revolution is really coming to the marathon. For one thing, athletes at race pace already struggle to consume much. Elites are frequently losing over 4% of their body weight over the course of a race. They're often getting only a few small gulps from each bottle before tossing it. Trying to get down 100+ grams per hour would be an extreme challenge.
It also seems that carbs are already a solved problem in the marathon. Evidence suggests that either carb loading or taking gels aids performance, but that both together have no additive effect. So it's very likely that athletes adopting best practices (as of the last few decades) are not experiencing performance limitations due to insufficient fuel.