Does MDM really reflect ECC?

I've come to understand that MDM is intended as the master data repository for a variety of R/3 (ooops, I guess it's called ECC these days 😊 data types (or I suppose we can say business objects), such as vendors, customers, materials and so on. However, in trying to figure out why business partners related to a customer were not deleted in the related R/3 system after having been removed from the customer master in MDM, I got the reply from SAP that "we do not send deletions from MDM to R/3. The reason is that MDM simply does not know how the data is used in R/3 - meaning if it is already part in any processes (like billing, and so on) or not. If this is the case, a deletion would completely invalidate and falsify R/3 processes. From an MDM perspective, we cannot do this."

Does this not invalidate the principle of MDM? Or is MDM more like BW; just an accumulation or snapshot of the underlying business data (from various R/3 systems), with more of a one-way communication?

I'm slightly confused here... but a newbie in the MDM world... 😉