Spot Bitcoin Exchange-Traded Funds (ETFs) are designed to track the performance of bitcoin with the custody of the asset being held by the ETF manager.
Bitcoin Exchange-Traded Funds (ETFs) are designed to track the performance of the underlying asset or index of publicly traded bitcoin mining companies.
The BlackRock ETF filing is a different bitcoin investment product than already exists on the market, but compares to a similar previous example: the GLD trust.