Rumours, I'd say.
Taking things apart and putting them back together entails work...Gubmint officials and manual labour don't go so well together
That snide remark aside:
They dont want to and they usually are not allowed to. Busting a 5 dollar
mod while inspecting it is one thing. Peeping under the hood of some hideously expensive lab equipment and breaking it in the process could result in them having to pay up for it.
So, if they want to take a look at the inner workings of something to make up their mind about it ( or checking for contraband ) they ask the consignee to come around and open/dismantle it for them. And laws almost everywhere entitle them to ask for just that if they deem it necessary.
I guess rough handling during shipping accounts for these occurences...