Thinking of myself at 16 and 20-22, I’m not sure that I would have been safer at 20-22 than at 16. In fact at 16, I probably would have been more likely to run home if there were a problem than at 20-22 when I probably wouldn’t have told anyone.
I’m not saying you’re wrong; I’m just thinking about how I think I would have reacted c”v. But I could be unusual and I could also be wrong about myself.
The thing to remember is that in communities in which it’s the norm, generally the parents are very involved and there is a strong safety net both in terms of the family and the community. So it may actually be safer than a 20-year old getting married in other communities in which people are more on their own.