1. The idea was to make an example of the company favoring cost effevtiveness over quality. which may not be bad ... but it should underline the cheap-assiness.
2. dtag is ofc present in frankfurt and at de-cix, with little capacity for public peerings as mentioned.
This and your 3/4 each make sense, as they represent a legit business interest for the different sides.
Hetzner preffering cheapass open and dtag preffering scalable private peerings.
Problem i see is Hetzner externalizing the cost of private peerings.
Which in return plays into 1. and the example of them externalizing other cost factors.