I've had the opposite experience actually, to the point that it doesn't feel like I'm doing much of a workout, but if I come along a group I might ride with them for the chance to get a
PR on a flat-ish section and/or recover a bit and/or get some protection from a headwind, I'm simply getting sucked forwards. However, my longest group-ride, a small group of 4 cyclists, has been just about
50 km long, and with the low effort that I felt I put in I would have done that loop at around 27 km/h avg solo, so I was surprised to see 30 km/h in the end, 31 km/h avg during the section between introductions and goodbyes, I mean, OK the speed was nothing wild but I ended fresher than how I started, which is what was wild to me. (During the small climb from Assas to Saint-Vincent-de-Barbeyrargues my speed is all over the place because two of the guys had been dropped and we were waiting for them.)
There is a GCN video with Conor Dunne, an ex racer and a giant, who maxed out at around 45 grams of exogenous glucose per hour, and he basically runs on carbs all the time. I suspect though that in the future there will be another video about how he managed to increase his uptake of glucose as a means for GCN to advertise some
personalized training service and sell yet another product. What you say about the carbs on the bike relates to insulin resistance for instance, but it doesn't solve the glycation issue for example, because the blood will carry the sugar and the hemoglobin in it will have more chances to get glycated, sugar is metabolically very active and has to be dealt with as fast as possible.
A probably better way: We let our body cover its whatever requirement in glucose from lactate, triglycerides, even-chain fatty acids, amino acids like alanine, and so on. If we are determined to punish our body by digging it into a hole for whatever reason, we supplement with 2 dates per hour.