[Blackbeard_]

They do try to mitigate this criticism in the first line of the article:

"Light-by-light scattering is a very rare phenomenon in which two photons – particles of light – interact, producing again a pair of photons."

This is the process that they observe (for the first time) whereas E144 observed the Breit-Wheeler process.

You can argue that this is too narrow a definition of light-by-light scattering but they have at least tried to make it self consistent...