Seat reservation for DB trains into Germany - different route if connection missed?

No the reservation would not be valid on the alternative route. (the reservations are only mandatory on those routes in the summer due to high demand) If you buy the reservation directly from DB you can get the reservation for 5,50€ from Amsterdam to Hannover.(they charge not per train but for the whole journey)

​@K in Oxford Looks like both the 16:38 train and the 18:00 one are still reservable for 1 July. (the earlier ones are already booked out in 2 class)

Thanks, Marvin. By ‘the earlier ones’, do you mean earlier ones than the 16:38?

​@K in Oxford yes.

Thanks a lot, appreciate it, Marvin.

Interrail also got back to me really quickly which is great. I’m asking if I’m allowed to share their response for information.

And I’ve bought the reservation for the latter ICE dir Berlin via OEBB.

They’re happy for their response to be posted here:

Different trains have different requirements for reservations. [but basically in this case both require reservations to get from the NL into D]

[re which connection to choose]  This is a personal decision, but if I were you, I would go for the later train. This is likely to cause less stress for you if the train is delayed by even a few minutes. That being said, when you disembark in Amsterdam, it is not difficult to get to the next platform. It is ultimately your decision.

[if I got the earlier Duisburg reservation but missed the train]  If you missed the train that your reservation was for, you would need to arrange a new reservation. Sometimes this can be done with station staff for no extra charge, but this is not guaranteed. If you miss your reservation due to a delay, we can send you a Delayed Compensation Request form. Once you fill this in, we can start an investigation to try to recover your lost funds.