If you understand what a checksum is then you know whether it is appropriate to use it. It is a type of hash, so sometimes it is appropriate and sometimes it isn't.

IMHO the business rules will dictate the usefulness rather than the collision probability.

I think it would be appropriate for BOL to point that out and either provide a reference to additional information or (2) explain how the aggregate is computed.

Good article though, created a great discussion, I'm giving you a 5 😎