Seized is mostly a legal term. Even though seizing bitcoin is only possible under the conditions you mentioned, in practice it is historically something that has happened many times. 

bullshit story to scare clueless nocoiners.
bitcoin cannot be "seized", only if:
- are on an custodial exchange
- you are too dumb to give them your keys

"seizing" some devices, it doesn't mean they seize also the bitcoin.

DarthCoin

Feels like there might be more to this story. 

Scoresby

bitcoin

Zhimin Qian, also known as Yadi Zhang, 45, orchestrated a fraud in China between 2014 and 2017 that left 128,000 people out of pocket.

She stored the proceeds in bitcoin, but UK authorities made a breakthrough in the case when they raided a Hampstead mansion in 2018 and seized devices from Qian holding 61,000 bitcoins, worth more than £5bn at current prices