"The most terrifying words in the English language are: I'm from the government and I'm here to help."
— Ronald Reagan








Therefore, you can stop believing that it is BlackRock or something similar.
The first transaction from this address was on May 8th of this year, when it started to receive BTC from the address 1JH...6kH, which was also owned by MicroStrategy.
Around 142 transactions were made to this new address, in a possible consolidation and update of the custody setup.
Right now, there are around 118,300.202 BTC($3,089,883,688 USD) in his possession. Which still doesn't match up with the total BTC held by Saylor's company.