The Dutch postal service treats letters and packages differently, and electronic greeting cards are processed as letters. They probably didn’t formally recognize letters could contain electronics.

Dutch bureaucracy also tends to have a lot of tolerance/leeway (gedoogbeleid), where rather than fix bad policies everybody just sort of agrees to do things a “reasonable” way. Attempting to fix bad policies can be seen as an expression of mistrust, a threat to whatever people have been getting away with so far, or general narc/snitch behavior. So even if someone realized that electronic greeting cards could be a threat vector, it would have been rude/socially isolating of them to bring it up and deny everybody on board their cute electronic greeting cards from back home.

The post office in our country became a bank, and then the bank-and-post-office was privatized and bought up and now the mail sucks and the former postal bank is investing in the Palestinian genocide (real estate on Palestinian land, weapons research with field tests on Palestinians, etc.).

So you don’t tell them to calm down, you just stay away. Hm.