If you can hear powder moving, it's not remotely compressed. And yes I can also hear crunch a few tenths after compression starts in a Creedmoor case (size included for reference, smaller cases have a smaller margin between no compression and crunch).
Because I shoot extruded powders in bottleneck rifle cartridges, my personal "red flag" on compression is when my COAL starts to grow with increased powder charge, and no change on my seater die setting. This basically means the powder column is resisting the bullet seating sufficiently that the bullet doesn't get as far down into the case. I'll always back off from this point, and break down those rounds.
I would NOT use this method on ball powders, or on any handgun charges with flake powder. Ball powder is highly sensitive to compression, you'll get a large pressure spike as soon as compression begins, and I can't really imagine getting enough flake powder into a handgun case to get compression without blowing the whole gun apart, but of course there's a cartridge and an action out there somewhere designed to do just that. People are people, and bigger is always attractive, even if it's not better...