Is this a bug? (Make Single User)

I duplicate an object (SHIFT+D) that already has IPOs. If I want to make those objects completely independent I tried using UKEY to make them single user and then choose the option Object & ObData.

Sometimes this seems to work fine. I go to NLA editor and choose keys for either of them and they are separated, but sometimes they remain linked and I have to go to the IPO editor and press the “Single User” button at the side of the IPO name.

Is this a bug or I’m missing something?