Your example is apples and oranges. Flock maintains private infrastructure that stores data.

If the DSLR uploaded them to Rent-A-Center owned/leased servers it would in fact require Rent-A-Center to take the necessary steps.

As Rent-A-Center would be the only group with proper access to data storage they would have inserted themselves into the chain of custody, and thereby have such obligation to ensure others data is wiped from systems they control.