You can bet that "undoubled" identical box made it unscathed a few thousand miles before UPS got their hands on it.
Double boxing is a courtesy..not a shipping requirement. Denon and virtually every other reputable CEM's shipping containers (boxes) pass every world-wide shipping reg that I'm familiar with (spent some time in the biz). Matter of fact, most of them are far more resilient and capable than the vast majority used for other goods.
You cannot excuse reprehensible shipping/handling practices by placing the onus on a vendor who does not "re-pack" a perfectly salient shipping container.
Don't get me wrong, double-boxing is wonderful, but the lack of it does not give a shipper cart-blanche to destroy adequately packed merchandise that lacks it.
Vendors and consumers have rights.
And as far as EE goes, they, like so many other low-priced online vendors, are able to offer such low prices in part, by NOT double boxing items, having a rather onerous return policy, etc. I'm sure with the volume they move, it adds up rather quickly.
There is always a price for the price.