Customs clearly has primary responsibility for container and general cargo inspection, but that responsibility can realistically be carried out only on a spot-check basis (at present, physical inspections cover about 10% of total cargo). It's my point that compliance by trustworthy operators with container content, verification, seal, and re-seal reporting is crucial, and constitutes a kind of "first-line" defense that customs must necessarily rely upon.
I agree with your perspective on the layers of security. And I completely missed your typo. :-)
The assertion that the port operator has "no responsibility" for security seems confusing, since they hire and manage the workers that handle the shipments, no?
Over here in knee-jerk, it certainly does seem a bit riskier to pay a country known to produce jihadists to run selected port operations, rather than someone a bit more reliably not-jihadist.