hum, in my base, the trains are with basic cargo full/cargo empty conditions and i've not been able to isolate a case to reproduce the same.
However if I change the conditions to "wait until", then I can get the trains to misbehave.

map originally done with creative mods, but disabled when saving ...

it is in my first post (below the screenshots)

I haven't been able to reproduce the issue when creating a test map with creative mod (even though the train network is longer than in my base), the trains go to all stations.
I've also tried playing around with the value train_stop_penalty (from https://forums.factorio.com/viewtopic.php?t=54042 ...

I'm fine either way, but isn't unintended result just another word for bug ?

I always found the 0.15 behaviour too good to be true, but without it, it does complexify a lot my current base.

I believe I have the same issue and I don't think it is explained by those bug fixes, and i've tested i can reproduce the problem on both 0.16.2 and 0.16.7

What is happening for me:
I have several green circuit outpost, each with:
. waiting area
. iron unloading station
. copper unloading station ...