Not strictly related to their study, but if we consider Solomonoff induction to be the most general model of all (albeit not computable), then I’d say yes to the question, if only because it will select the most specialized model(s) for the particular problem at hand automatically.

One could argue universal general intelligence is simply the ability to optimally specialize as necessary.

I think one aspect that is overlooked when people are involved is that we create specialized or fine-tuned models precisely for the reason that a general approach didn’t work well enough. If it had, we would have stopped there. So there’s a selection bias in that almost all fine-tuned models are initially better than general models, at least until the general models catch up.