No, I believe it shows marginal improvement only.

  Opus 5.5 to Model 3 early -> +2.1
  Model 3 Early to Model 4 -> +2.3

If Fable 5.2 is Model 3 rather than Model 3 early it reverses to +2.3 vs +1.7.

Based on the score it should be Model 3 rather than Model 3 Early, to me it's not entirely clear based on what it says about the tested Mythos 5.2 being a different checkpoint than the public one.

In any case, we aren't talking about a big leap in score unless further benchmarks narrow the CI, I remember that the Model 4 score supposedly came from fewer benchmarks.