I know of many adults who experimented sexually as children (not with adults) some as early as the age of six. This is not normally classified as "abuse" or at least not in the 1950s. They experimented with both sexes and yet almost all (around 99%) ended up heterosexual. Mind you this is personal relationships and not some foundational study. It is from my own personal experiences that I draw my conclusions from they are not spoon fed to me.
It says they started off with about 13,000 people surveyed between 2003 and 2006. 98% of the participants in the study identified themselves as heterosexual. It also doesn't mention having any "results in mind before the study was started." It would surprise me if they were not asked a whole lot of survey questions, and these particular correlations were found to be statistically significant.
But possibly you have read the study itself, and not just this very brief press report? I'm interested. Do you have a link?