Yes. Due to Block Exemption, MB UK were able to practically impose a ban on sale of genuine MB parts outside of their franchised dealer network. This is a concession to car manufacturers, in return for which they are forced to supply parts, special tools, diagnostic equipment, and access to computer systems for non-franchised garages. They have put in a provision where garages that buy genuine MB parts under Block Exemption commit to not sell these parts other than as part of a service or repair that they carry out themselves, or they risk losing access to MB parts and other resources. The end result is that genuine MB parts are only available for purchase from franchised MB dealers (some of them have an eBay store).
That said, you do get the odd genuine MB part that pops-up on eBay from time to time, as a result of some independent garages 'offloading' genuine MB parts to eBay traders via the back door. But this practice is not very common (because it will attract 'unwanted attention' from MB UK...