Unfortunately i'm not an expert, but i feel this statement might prove the exact opposite of what it is supposed to prove. More functional muscle mass, to me that sounds like his muscles being more efficient than before. If they are indeed more efficient now... wouldn't you need less muscle mass in order to achieve the same, instead of more? If the theory is that his muscles are now even stronger in relation to how much they weigh, that it has become beneficial to have more, even uphill, then why stop at 63kg? We saw what happened in Valencia, so clearly it isn't as straight forward as that.
If someone with some authority on the subject could shine a light, it'd be appreciated.
He's not describing weight loss without power loss. He's trying to explain why Evenepoel now needs to be 3kg more heavy than the years before.
There's an optimal development curve that's based on his physiology, goals, that assesses how he can get the most out of his natural abilities and where he has the most room for improvement in terms of his physiological development.
To get to 60kg it would take a few years (2-3+) and the problem is that we get past 18 humans have a hard time staying the same size. Remco would lose too much power at 60kg and he'sd be much more prone to illness, injury, the elements then at 63kg.
Yes, he cannot get too big otherwise he's on a suboptimal physiological development curve for climbing.
His optimal weight might be 61.5/62kg but he gets stronger and older it becomes much more difficult to reach that weight and it takes more time to do it in a healthy way.
The implication is that while 60kg makes it much easier to climb his body cannot feasibly work optimally at that weight at his age.
This was a constant concern when I coached wrestling. The power to weight aspect was critical. I had a kid cut weight to the 50kg weight class from his normal walking around weight of 60kg. He had a big advantage at 50kg he was not in the most efficient power to weight zone. He ended up performing the best at 54 kilos because he was in his peak efficiency zone where the power to weight ratio was maximized.
Had the same thing happen with a kid who was about 82 kilos at the beginning of the year and we wanted him to wrestle at 77.5 kilos and he wanted to go up to 86 kilos. He struggled initially at 86 kilos but once he got acclimated there was no way he could stay at 77.5 kilos because we was 1.96 meters tall and the drop would take him far out of the optimal power to weight ratio.
Any cut below 63 needs to be done as a long term cut and that's only if Remco remains in his sweet spot while making that cut. He'll near the end of his maturing phase and then they'll be able to plot what weight he should be at and how to get there with the maximum amount of power, acceleration, etc.