I have also used this for years, and my partner never once didn't manage to withdraw. I didn't get pregnant, except when we stopped using the method, both times I was pregnant within the first cycle so no fertility issues or 'luck' in not getting pregnant when using it.
I used it knowing it was not 100% effective, and we were both ok if I did get pregnant, but it actually was very effective and we had to make more of an effort to really get pregnant by not using any method at all.
No, this is not the same as a natural family planning method, we used it all the time.
I would not recommend it though, to anyone not happy to have children, because of the STD risk and the lower risk than, say, the Pill. If you are in a long-term relationship, both happy to risk getting pregnant, but don't have a set timescale or want to right now, then it's fine as a method of managing fertility.