That's the regular A350-1000. This is the A350-1000ULR, which has an additional 20,600 L rear tank.

https://www.airbus.com/en/newsroom/stories/2026-07-extending...

Looks like they updated the article to say 20,000 litres of additional fuel, it wasn’t like that before as what I posted above was a copy paste.

Edit: it actually says at the bottom:

  (This story has been refiled to add the dropped word 'additional' in paragraph 8)