Avalanche is indeed a good L2 coin but I don't find any direct implication on the post or the articles how Larry Fink supported it.
What I do liked about his assessment is comparison of bitcoin with gold. Both of them are verifiable and universally accepted and limited in quantity. Though the exact quantity of gold can't be verified, we have an exact number for bitcoin. And with more and more people holding bitcoin as such or through ETFs, the liquid supply of it would decrease resulting in a higher price.