Its closure is also mentioned in the text: "After the 2019 closure of the Puttgarden-Rødby service between Germany and Denmark and the seasonal Sassnitz-Trelleborg route linking Germany and Sweden in 2020, the Intercity is now the last one running."
BTW. I was on the Hamburg-Copenhagen train on the Puttgarten-Rødby ferry in 2015 during the height of the Syrian refugee crisis. I had changed my booking to earlier trains because of expected delays. It and connecting trains were packed, as were the train stations, also with immigration officials and volunteers. Brings tears to my eyes to this day.