[hehaheha]

Because passive does not necessarily mean index. You can be passive and concentrated (see ARKK). And more importantly real world indices are moving target to begin with. They’re just very rough approximation of market basket. SPX is not representative of market as it relates to mpt at all. In fact that’s likely one of the biggest myths in modern finance.

[xyzelement]

The fact that Arkk's own website refers to itself as an active equity etf should prompt you to reconsider your definition of these terms.