Two things to consider
First:
Up to 60% of all US teens have HPV so if 10% of Teens who tout abstinence do not then there is something significant.
Of course not all teens who claim abstinence follow through but if they are doing 50% better than teens who do that that proves ‘they are not all going to do it anyway’
Second:
As someone else pointed out schools and media have tried to redefine ‘sex’ by limiting it to the strictly penetrative test.
In fact Sex is so much more and some might think ‘this is not really sex’...
BS. 24% of 14-19 year olds as reported in Dunne EF, Unger ER, Sternberg M (2007). "Prevalence of HPV infection among females in the United States". JAMA 297 (8): 8139.