That is not a model-specific claim, it's a claim on the nature of LLMs.
For your argument to be true would need to mean that there is a qualitative difference, in which some models possess "true reasoning" capability and some don't, and this test only happened to look at the latter.
Furthermore we have clearly seen increases in reasoning from previous frontier models to current frontier models.
If the authors could /did show that both previous-generation and current-generation frontier models hit a wall at similar complexity that would be something, AFAIK they do not.