I believe you immediately. During our house renovation, a lot of botching was done in many places. Before we have the facade painted next time, that will be corrected.
If you choose the beautiful wood-aluminum windows, it would be a shame to just slap aluminum windowsills on them. Why not choose nice granite windowsills? They look great, last forever, are easy to clean, and even during hail you don’t hear anything (on the windowsill). Available in dozens of colors and finishes (preferably polished).
Normally, anti-drumming mats are glued underneath (something like Armaflex but with bitumen). It's like day and night. Then you hear the rain more on the damp earth than on the windowsill. Presumably, at they were "forgotten" or simply not proactively commissioned and also not proactively offered.
Usually, (also) perfectly installed aluminum window sills with anti-rattle coating, decoupling (= e.g. rubber sealing between window and window sill, ...) suitable substructure/mounting/thermal insulation are still measurably/audibly louder compared to stone window sills. Often larger stone mass = better sound insulation.
Note: Modern windows well-installed "thick" dense windows dampen exterior noise of the window sill usually significantly better than before, so that one often (only) for this reason (almost) never hears anything from the rain.