A couple of rides are hardly enough evidence to support a whole diet, there are way too many variables to draw conclusions from just 2 rides. Furthermore, if we just want to look at fast rides, I'd guess that the overwhelming majority of riders were fueled by carbs. If I look at best results on long gravel races or marathon XC events, there is no way I could've replicated those efforts on walnuts.

As far as the protein intake and supplementation, it really depends on your activity levels. With a low enough training load, you're probably fine with the .8-1.1g/kg of body mass or whatever's recommended nowadays for the average adult. In my case, I'm doing 15+ hour training weeks, 1-2 gym sessions, 1-2 intensity/interval rides a week, etc...I just wouldn't be able to recover this on 70ish grams of protein a day.