Those custom made scramblers (XOR keys) made with bit errors (unsupported ECC), so they don't make lot of sense when it comes to data recovery, mostly for database statistics and controller analysis.
In many cases you can extract the scrambling pattern right from the dump with data. Very often block with LBN=0001 stores zeros (scrambled).
Boolean XOR operation works this way:
A xor 0 = A
For the block 0001 this "A" = scrambling pattern.
This is possible because nowadays distance between MBR and Boot record is more than 1 virtual block of NAND physical image (not 32/64 sectors).
Even if LBN0001 have some data (not zeros), it's possible to find several blocks where some pages filled with scrambled zeros.
Merging 3 or more (odd number) blocks through "Bit verificator" operation you can extract pure key.

Diagonal pattern is a virtual block with pure scrambling pattern (XOR key)