The problem is that the max path is enforced even for intermediate paths during cooking, even if the “final” filename would fit in the limitation (which is no longer an issue on modern Windows, for example). During cooking Unreal stages the files in the Saved/Cooked/WindowsNoEditor folder, putting your assets 28 extra characters closer to the limit. There should be a setting to detect whether the OS supports longer paths and only check the length relative to the assets content folder in such cases, not the whole thing.