difference between ultimatum and boundary

I had told my husband, from a genuine place of love, that if he kept crossing my boundaries, I would leave. That even though I love him, I would leave. Then, he came back and said he would do what it takes, because he didn’t want to lose me. It’s been months and he’s sticking to his word and seems to be joyful about it (vs resentful). I feel like I came from a place of setting healthy boundaries, yet when I think about it more, it seems I set an ultimatum. But this situation feels different that that. It feels like he is taking action from a place of love…not “just” fear…and I came from a place of love. Is that the basic difference between an ultimatum and a boundary?