Progress bar would be indeed much better. And harder to code. But not much. I remember doing very simple and just 2 hor. lines high one for my movie playback. So, it did not hurt screen content much. About 40 lines of ASM code, very low CPU time usage.
There were diverse progress bars for loaders - by Spectrum and Atari ST too. But I don't remember seeing progress bar used by depackers.
Famous Schrodinger's cat hypothetical experiment says that cat is dead or alive until we open box and see condition of poor animal, which deserved better logic. Cat is always in some certain state - regardless from is observer able or not to see what the state is.