No, I've never seen someone drop to assy due to something as simple as not understanding typecasting. Historically it has been for speed (used to be common, a lot less common now) or to do something the compiler/language doesn't support. The anecdote falls into the latter class, but only because the original code author didn't understand C well enough.

When I started programming, the running joke was "you can write FORTRAN in any language, some are just more difficult."