I sent an e-mail this morning to Eurobonus and got an e-mail back within two hours.
I am very impressed with the efficiency at the Eurobonus UK office, they always get back to me in no time.

The reply was this:
To be able to establish if points can be credited for a certain
Eurowings flight we also need to know the Lufthansa flight number.

Any idea what that is supposed to mean?

My initial thought is that only some Eurowings flights and eligible for EB point earnings. That seems to be the most logical answer.

Although, since I never actually booked the Eurowings flight I won't bother to find out at this stage.