From looking at the code, it seems like SNikon’s fix is implemented in the latest Preview and has been in since before 4.12 branched off of Master, meaning that it was in 4.12 the entire time.
As for what was checked in, as SNikon mentioned in his Pull Request, only the edits to K2Node_VariableGet were intended so the other two edited files were ignored. When .Oconnor committed these changes, he created a function called RestoreSplitPins instead of just using one implementation of this code and called that where SNikon’s code would have been along with a few other places.
If you’re still experiencing the issue that this was meant to fix (UE-27652 for my own reference) then please let me know and I’ll see if I can reproduce it soon. If so, we’ll need to get that bug report reopened as it is currently closed due to this fix.