So what exactly is the difference between those and the ones Amazon https://www.amazon.com/OnePlus-Buds-Wireless-Earbuds-Chargin... says I can get tomorrow for $79?
I’m fairly certain they are the exact same ones confiscated. It’s a near blatant knockoff of Apple’s patented designs. Now should Apple be able to get said all encompassing design patents? That’s a different debate.
If these buds were seized as counterfeits, then there had to be an express intent to sell these as imitation Apple products, which I find rather hard to believe (for starters because the packaging isn't the same). Also, when producers remove any brand markings, like logos and other distinctive material unique to that company, knock-off/imitation cases are always weak. For good reasons too, just as with trademarking generic names. You don't want a single company to dictate the use of generic things.
Maybe most import is that this seizure will unlikely have happened on a whim. Almost certainly, somebody has requested for this to happen. That itself should give rise to some serious questions. Because it would likely make this a rather blatant (and probably unlawful) case of economical warfare.
To use the extraordinary powers of border guards for that purpose, without any court case, is downright corrupt. Like mafia style corruption. I wonder which highest ranking official signed off on this. That person has some explaining to do, for he/she just made the USA look like a tinpot dictatorship. Ignorant too, to boast about it on their web site. Unless that's done intentional, as propaganda to convince the locals this was legal or good "to protect America". People abroad will likely have a very different view on that.
What the American government often forgets, in its self-centred and mostly domestic focus, is that the rest of the world is observing things like these. Behaviour like this always has consequences, even if it can take a while.