I think changes in air resistance is of negligible importance between riders. How well the riders are currently adapted to altitude and less oxygen should matter far more.
Above ~1,500 m above sea level as is the situation for upcoming worlds, you can only just start to have measurable effects compared to a similar event at sea level, especially if you are not acclimatized.
It seems like 1995 Duitima has been completely forgotten here?
The route between Tunja and Duitima took place between (afair) 2550-2850 m above sea level.
Consequently MUCH harder for the body, especially in longer efforts: VO2max drops, you get higher heart rate (for a given power), you increase pulse and lactic acid faster, and recovery often takes longer and therefore performance-limiting for even well-trained elite level.
Regarding the aerodynamics and an extremely streamlined low-slung style like Remco vs. a much more upright position.
In a strong headwind, Remco has a colossal advantage.
In thin air and calm, the possibility of total air intake, VO2 max and overall total oxygen intake has a colossal advantage in the latter terrain.
The 2025 Rwanda ITT is not the 1995 Duitima ITT.
And if there turn out to be strong headwinds, Remco will still have a much greater advantage in Rwanda than if he were in his prime in a 1995 Duitima ITT.