It’s not
total bullshit mate.
What he’s possibly referring to is Raman spectroscopic scanning devices. They can be as small as a handheld device similar in size ish to a traffic cop’s speed gun & with the press of a button, can identify
all compounds in a powder, solid, liquid etc form in a few seconds & can even scan through opaque glass & plastic packaging - so yeah, a point & a click & Customs know exactly what is in a vial / tablet etc.
Whether they can scan through multiple layers of non opaque materials such as parcel packaging, I don’t know but
@janoshik probably does.
Just to add, Raman scanners are very common with LE in Western countries & you can pretty much guarantee that Customs agents at every port of entry to the continental US (for both people & trade goods) will have access to them as & when necessary.
In short - “stealth” packaging is obsolete & worthless if whoever is examining your package has a Raman scanner.