All items entering the EU and originating from the UK can be subject to Customs checks - doesn't mean they'll check every parcel coming into your country, but if they do and there's a fake Rolex inside you'll have problems - especially if you are in Germany or France.
So basically the TDs provide the best way they know how to get the package entered into the EU; however, if the package is confiscated, they are not responsible, we the buyer bear the risk, is my understanding correct?