I agree with oomis. The first time i ever heard of this shtar was when my friend broke off his engagement, and one of them needed to write this shtar. Never figured out why it was needed or how the process is worked out.
Regarding this shtar, since it is made to be mochel another, do you need it for a divorce as well? It only makes sense that you should, since according to most people (there are people who argue as noted in comments in this post and others)that divorce is worst than a broken engagement.
Do you need a shtar if you went out with a girl multiple times and it didn’t work out?
Oomis1105:
IMHO, I think the rabbonim made up this shtar because they saw that shidduchim engagements were unraveling and they wanted people to feel better afterward. I never heard of it and I’ve officially been dating for 3 years. And when my older siblings and their friends were dating (about 7 years ago)this concept of this shtar was unheard of (but then again so was some of the interesting things that occur through the shidduch process now also were unheard of then).