I think it only truly needs that for password protected files. You'd have to try it out to see.

Make a directory like 'missing_modules' somewhere and in your code do use lib 'path_to_it/missing_modules' before use Spreadsheet::ParseXLSX, and in that directory make a Crypt/Mode/CBC.pm that just contains 1. Then run your code and see what other modules you might need to pretend exist, and see if it dies trying to call any nonexisting subs or methods.