I doubt US customs is secretly spraying something toxic on imported cannabis/hemp seeds, which are fully legal in US at federal level.
How would customs do it, contaminate the seeds? Aren't commercial seeds shipped from Europe in their final sales-unit packaging, such as packaged in Spain or Netherlands, and these shipped in bulk internationally to distributors?
For ex., back with Dinafem, were the seeds destined for US distributors actually imported in bulk and the seeds packaged at a central US Dinafem or contractor facility, and then shipped to US distributors (vs. end-user English language packages shipped from Europe direct to the US distributors)?