I'll thank you to quote me accurately and not twist my words merely to make yourself seem correct.
I did most emphatically NOT say a metal bracket WOULD bend or break if packaged unsupported. I said it was AT RISK of breaking if packaged unsupported.
As a trained engineer, surely you appreciate the importance of reading something carefully, and paying close attention to nuance and detail. Even if you're not currently demonstrating much skill at that, I assume it's something you were taught at some point.
Obviously a metal mount would be much more durable than a plastic mount, no matter how carefully such a thing as 3d printed, but they aren't invulnerable. In my experience as the grandchild of Alberta rednecks, it doesn't take much of a drop to ruin a scope mount, either. No, my family has never dropped a DL-44 replica. Yes, my family HAS dropped any number of Mauser-action rifles, mostly with scopes attached, and yes, the scope broke first but many of the mounts were damaged too.
Anything sent through the mail is going to be subject to handling and abuse beyond the sender's control. Ensuring nothing in the package is left unsupported is always a good idea. The part of the prop that was surrounded by foam is fine, the part that was not is damaged, and the original poster has acknowledged my suggestion without showing signs of offence so I'm not sure why you even needed to stick your oar in.
By all means offer us the benefits of your professional knowledge, regarding the durability of certain materials or anything else you have experience with - but don't put words in my mouth just to make your argument seem stronger. It doesn't do that, it just makes it obvious you're not paying proper attention in the first place.