I believe a lot of this is just an attempt to make up for what the language lacks, in this case it lacks stronger scoping and typing systems. It would be a bit of a pain to create a SanitizedString type for a sanitized string that is only used in two functions, but this is a good compromise between speed and efficiency. It may not always be the right trade off, but that's how trade offs work.

Granted, the SanitizedString type is checked by the compiler, while the s* variable name is checked by the programmer, each having its own problems.