No, it has not changed. Note, you will not get upgrade points for a slave that was bought from a slave guild. The guild will tell you in advance if you will get some and a rough reason why you will not.
There actually is a change/bug here - the text saying you will get upgrade points requires >= 80 obedience, but it requires >= 90 to actually give the upgrade points when selling.
Good catch, the value was 90 in older versions of Strive but was reduced for consistency with other parts of the game. Seems that it was partially reverted in the mod at some point.
