I don't think the numbers really add up to much at the moment. 32 men? That's not nearly enough for a study to even begin to be valid.
If we look at today's western culture, I think it's safe the assume that the vast majority of men have phones, and for large portions of time are carrying those phones in their trouser pockets. The world populates at ever steady rate, sperm does not seem to be effected by the last 10+ years of ever increasing usage figures.
Alternatively, you could say 100% of men with testicular cancer, or poor performing sperm, have phones in their pockets, as they probably did.
I don't think much is to be taken from this study. I agree it justifies further study, with greater numbers, tests and varying factors. However right now my phone is going right back in my pocket without hesitation.