Apparently, the new ActionScript Compiler 2.0 no longer supports the old [frame] metatag which allowed you to add preloaders to pure actionscript projects.
I've verified this IntelliJ - switching the "Prefer ActionScript Compiler 2.0 for pure ActionScript build configurations" makes a difference between the preloader being instantiated and executed, and the main class being instantiated and executed.
Googling yield no result, so is there currently any way around this issue - use ASC2.0 but have the benefits of the Frame metatag?