I don't know what you mean by "when adjusted for battery size". Do you mean it takes the same amount of time to charge an SR+ or an LR? That sounds about right to me. However, you get more mph with the LR and the power the car gets from the supercharger is also significantly higher in a LR (250 kW vs 170 kW).
Given these numbers I find it misleading to say they charge at the same speed just because it takes about the same time to reach a certain SoC.
What is relevant in regards to OPs question is that a LR pulls much more power at least from a V3 supercharger. Thos does lead to more heat that needs to be dissipated, thus the louder fan noise.