Here is his explanation about that point:

But you are going to get stuck in Germany!

No.

“But its trains are unreliable!”

Yes. But still no.

It goes like this. This trip takes me through parts of Europe where timetables are thin. Very thin. If anything goes wrong there – a tree on the line, a broken down train – I am screwed. Stuck. For hours. Between Kemijärvi and Kemi there is 1 train a day. Kemi – Haparanda, 2. Boden – Umeå, 4. Lyon – Barcelona, 1. Madrid – Badajoz, 2 useable ones. Badajoz – Entroncamento, 2. And in Boden and Entroncamento I have really tight connections.

And then, bizarrely, the thinness of those timetables in France, Spain and Portugal, and the absence of night trains in those countries, leaves me without any serious worry crossing Germany – because I cannot do more than Strasbourg – Madrid in a day, and Madrid – Lagos the following day, even if I wanted to.

If the NightJet 471 I need across Germany is cancelled, I have (albeit uncomfortable) trains I can take instead. If the NightJet is delayed, I can get off earlier than Offenburg (probably Frankfurt) and have other options there. Trains might be unreliable, but the timetable is dense, and there are loads of diversionary routes. And last but not least, pretty much no trains in Germany are compulsory reservation, meaning I can just go take any train. Were I to need something else in France or Spain, where everything is compulsory reservation, I could likewise be unlucky that the train I need after a disruption is full and I cannot board.

In other words, Germany might cause plenty of disruption, but it also copes better with disruption than pretty much any other country.

Literally right through Germany 😂😂 RIP

Longest train journey gets even longer. That's a win.

Lol, he's not going for a speed record just a completion record.