i think what's happening is that ls is reporting the logical file size in the "size" column and the sum of filesystem-reported physical file sizes (with various forms of overhead) in the "total" row
this then combines with XFS doing something weird (not consolidating extents promptly? not sure how XFS works internally) which happens to inflate file sizes under whatever write pattern wget is performing, until wget closes it and i do a mv and the filesystem optimizes the way the file is laid out on the disk
i think ls is wrong and the choice it makes is actively confusing, but it is probably not nearly as noticeable on ext4 or a lot more people would know about this
