IIUC, this is not a survey of the *level* of sexual assault, but of the rate. And if the sample questions quoted above are typical, then I'm surprised that it isn't higher.
OTOH, the questions that were listed above (in the discussion about poorly worded questions) don't distinguish between a bit of uncomfortable humor and forcible rape. One presumes that actual criminal activity is rare, but this isn't evidence of that.
That said, in groups that are predominantly male and relatively isolated from external contact, one might expect that undesireably agressive sexual behavior would be relatively common. The real question to me is how moderate is the degree of undesireably agressive sexual behavior. (The rate would be interested *IF* coupled with the degree.)