I’ve heard that too. But I’d also imagine that would have been much more difficult to do in nineteenth century Utah, where I’d think able bodied Mormon men were probably at a premium regardless of their marital status.
I realized as I was typing this, that some of the answer could be that in the 1870’s a significant percentage of Mormons were probably converted from somethign else seeing as how the religion itself isn’t much older than that, which would explain the gender disparity.