It could. If he has 2 cards. Say 1k limit on each. 100$ debt on 2K credit is 5% while 100$ debt on 1K credit is 10% utilization. Big change in the calculation for score.
But again, have the CC companies even had time to report that info to Credit Karma, etc? Doubtful.
Putting 100 on a credit card (or 100 apiece on 2 credit cards) in and of itself isn't what's going to affect your credit. Not paying it when it comes due certainly could.....and even then, a 30 point drop sounds excessive. Again, I think we're missing some key points in that story.