It's more than that. Both Angband and NetHack are forks of their ancestors.
There is an unbroken line of continous development of the same code base coming from the 80s. Hack and Moria OTOH were clones of Rogue and didn't share any source code with it.
There is still non trivial code from 1984 in NetHack: https://i.imgur.com/H4HpjYf.png
With Angband, the case is a bit more complicated as the original Moria was written in Pascal but it was already converted to C in 1987 and Angband decends from that code.