Why a monolith is differentA full-size card with chips on a board gives the bench a flash chip to remove and read. A microSD gives nothing to remove. The coating on the back is taken off to expose a grid of tiny test pads, each pad is identified against a pinout database or by probing, a needle adapter or fine wires connect to them, and the raw flash is read out around the dead controller. One recovery house puts it at fifteen to twenty needle placements on a typical card. The raw dump is then descrambled, its error correction and its page and block order solved, and a virtual card assembled from it.
Where the data is, and how it is scrambledInside, the controller spreads writes across the flash to even the wear, keeps a cache of recent data in a faster region of the same flash, which on a SanDisk card one laboratory measured at a fifth to a third of the capacity, and scrambles everything with a key of its own. SanDisk, Samsung, Phison and Silicon Motion each have their own scrambling, error-correction and page-ordering schemes, and SanDisk's flash speaks a different interface again. The bench's software knows them; that is most of what you are paying for.
Snapped cardsA microSD that has been snapped, bent or chewed is recoverable if the flash die inside is still whole and only the package and the pads have broken, and the bench can usually tell from the first look. A die that has itself cracked through is beyond anyone, and you are told so, with nothing to pay. Send every piece, however small.
FakesA counterfeit card is a small flash chip behind a controller told to claim a large capacity, usually under a SanDisk or Samsung label. It works until you write past the real size, then files vanish or come back as garbage. Everything written to the real flash is recoverable; everything written past it was never stored. The free look measures the real size, and the card is read as what it is.