that linked article had many exampled positions with many different allocation amounts.. picking just the highest("EXTREME") mentioned is not what blackrock concludes.. their actual conclusion is a 3% position of btc allocation not 84.9%
also reading through other commercial banks desires to hoard bitcoin via the BIS settlement network agreements. they too want more then 2% but less than 5% ability to hoard BTC

and if you ever look at any investment institution none of them have high % hoarding of one asset. they all spread their eggs across many baskets with a sub 5% hoarding per 'egg'