So what you're saying is, for cryptography software, "Agile" development doesn't work. For cryptography software you need very careful, deliberate, up-front design. You need careful, deliberate implementation that does not deviate from the design. You need careful deliberate validation.

What we may be seeing is that we have roughly a decade now where "Agile" has been drummed into developers as the best way to write software. Perhaps it's the only approach they knew to take.