Which of these statements doesn't describe Flash memory?

Flash memory cannot be erased byte-by-byte (it must be erased in blocks) and it is not constructed from logic gates like NOR gates, but rather from floating-gate transistors. While NOR Flash exists, the 'NOR' refers to the cell interconnection architecture, not the use of logic gates to design the memory cells.

Step-by-step Derivation:
Step 1: Analyze Option A. Flash memory is organized into pages and blocks. While reading and writing can sometimes be done at a finer granularity, erasing is a high-voltage operation that must be performed on an entire block of memory. Therefore, byte-wise erasure is impossible. This statement is false.
Step 2: Analyze Option B. Flash memory has a limited number of program/erase (P/E) cycles before the oxide layer degrades. While it is rewritten, it is not designed for 'frequent' rewriting in the sense of high-endurance RAM; however, compared to ROM, it is rewriteable. In the context of 'incorrect descriptions', Option A and C are more fundamentally wrong.
Step 3: Analyze Option C. Flash memory is built using floating-gate MOSFETs. 'NOR Flash' and 'NAND Flash' refer to the wiring configuration of the cells (resembling NOR or NAND logic gates), but the memory is not 'designed using NOR gates' as logic components to store data. This statement is technically a misdescription.
Step 4: Evaluate Option D. Since both Statement A (byte-wise erase) and Statement C (designed using NOR gates) are incorrect descriptions of Flash memory, Option D is the correct choice.