Compared to my Shih Tzu, yes. And mine is just 1/2 Yorkie. She is quite stubborn. heheheh.
She is 1yr4mos old yet she is only 90% toilet trained. She still goes on pads when she feels the urge, rather than ask us to go out- unless it's convenient for her. My Shih Tzu was trained by 5 months, and did not need pads anymore after that. I think it's all in the personality of the individual dog though, maybe not totally the breed. But mine is stubborn. I love her & won't trade her in though!
I still hold out hope, because she gets better then regresses, but is a bit more better about pottying. But it's all about her convenience, not ours. Whereas my Shih Tzu it's all about us. So just two totally different breeds I'm comparing here. I'm no expert, just relaying my opinion from my personal experience.