The article is new, only the tested CPU+GPU is from 2019.

Snapdragon 855 was indeed the chipset used in most flagship Android smartphones of 2019. I have one in my ASUS ZenFone.

Based on the big ARM cores that are included, it is easy to determine the manufacturing year of a flagship smartphone. The cheaper smartphones can continue to use older cores. Arm announces a core one year before it becomes used in smartphones.

  Cortex-A72 => 2016
  Cortex-A73 => 2017
  Cortex-A75 => 2018
  Cortex-A76 => 2019 (like in the tested Snapdragon 855)
  Cortex-A77 => 2020
  Cortex-X1 => 2021
  Cortex-X2 => 2022
  Cortex-X3 => 2023
  Cortex-X4 => 2024

Ok. Cool, but the title makes it clear which one it's talking about. Usually when a date is added to the title it's in order to clarify when the article was published, not necessarily when the object of the article began to exist.

I didn't realise the cores in the Pi 5 were 4 years old already. Surely if some vendor like qualcomm or mediatek released a sbc with decent software and recent cores, they could sweep the floor.

They are 16nm, so yeh, "old". Newer tech means a newer node and considerably more expensive. At which point, why are you buying an SBC over some small intel/amd thing?