That's not relevant. Over a Deutsche Telekom phone line you can choose an ISP. The ISP sometimes has a layer two connection to you and therefore has their own infrastructure or they have a layer 3 connection in which case you suffer from the Telekom policies.

Layer 2 = their infrastructure connects you to the internet

Layer 3 = theyre literally just a reseller, DTAG is providing your internet connection, the ISP just billing etc.

That's too many words for simply saying "The fastest available DSL is 16Mbit/s and the customer service will be rude and useless".