In a recent talk [0] Francois Chollet made it sound like all the frontier models are doing Test-Time Adaptation, which I think is a similar concept to Dynamic evaluation that Gwern says is not being done. Apparently Test-Time Adaptation encompasses several techniques some of which modify model weights and some that don't, but they are all about on-the-fly learning.

[0] https://www.youtube.com/watch?v=5QcCeSsNRks&t=1542s