This is moderately weird. As I understand it, some of the attraction of BTC is the hard limit on it. Which makes it deflationary, but that's a different topic. Why would BlackRock say something contrary to what everyone else has been pushing?

They're absolutely right. All it takes is for the code to be changed and node-runners to update their nodes with the new limit. It could literally be done overnight. They could even add an air-drop feature to fairly and evenly distribute the extra bitcoin to everyone around the world who doesn't already have some bitcoin so that everyone has the same amount.