The file size is the giveawayThat small JPEG inside every NEF, CR3 and ARW exists so the camera has a picture for its rear screen. An ordinary tool lifts it, marks the RAW recovered, and goes on to the next file. A 50MB frame therefore comes home at 5MB.
Big files are rarely in one pieceFree space on a card is rarely one unbroken run long enough for a large file. Reach the first gap and a basic carver stops there, which costs you the corner of a JPEG and the whole of a RAW or a clip. Which run follows which is recorded in the file format, and reading that is the difference.
Each RAW format fails in its own wayTIFF underlies CR2, which is why it takes damage fairly well. CR3 sits in a newer container built along different lines. On a NEF, damage usually shows as green and purple banding across the picture. ORF, RAF, RW2, ARW and DNG each need handling on their own terms, and no shop-bought tool covers the full set.
What deleting actually doesOn FAT and exFAT a deletion simply releases the file's cluster chain, and a format releases the lot. None of it is wiped from the card, which is why recovery is possible at all — and why the very next exposure may land straight on top of the picture you wanted.