Currently drag and drop expects to selection to be in the same folder, but blender internal file browser allows to select files from different folders when recursion is active. When writing to operator properties the `directory` is taken now from the first file provided, and `files` are now relative to this `directory` instead of just taking the file name. When reading from operator properties filepaths are normalized. I notice this issue while reading about #140942, the issue would require a proper fix too. Pull Request: https://projects.blender.org/blender/blender/pulls/140948