I've heard from a couple of people and from sonarqube's flash static analysis tool that

"In ActionScript 3, constructor code is always interpreted rather than compiled by the JIT at runtime, which is why the body of a constructor should be as lightweight as possible. As soon as a constructor contains branches ("if", "for", "switch", ...) an issue is logged."

Does anyone know if this is more than just rumor and superstition? Is it old knowledge, or is it still true? Does it apply to Flex/AIR mobile builds too? I can't find any sources newer than 2009 discussing it and even those aren't very in-depth.