BEP 47 introduces among other things, padding files.

Not supporting this for torrents which make use of this feature (e.g. most new torrents at the Internet Archive, at least post-2020) can result in aria2 trying to actually fetch these files, which will result in errors or forever being stuck in a leeching state waiting for these files that aren't actually meant to be downloaded. Additionally, these padding files can take up a significant amount of space depending on the amount of files & the piece size.