At first glance that struck me as a typo with a word left out; For example "...having had UNPROTECTED' anal sex..."
Obviously, that's just conjecture. Another possibility would be lack of honesty by those homosexuals reporting. But, perhaps there is an entire group that doesn't receive anal sex but only gives anal sex.
Here’s the next paragraph:
“The CDC reported that during the same period the proportion of men reporting having multiple sex partners and unprotected anal sex increased from 23.6 percent to 33.3 percent.”
It appears that “only” 61% participate in anal sex.
I suspect the rate for oral sex approaches 100%.