The premed has made his specialty decision based on limited experiences from shadowing, reading SDN, interactions from family members who are Drs, etc. This isn't the same as 3rd year rotations when you are in different rotations and start to get a feel for different specialties. Chances of matching into a specialty is also based on the application (board scores, research, rotations grades, etc). If you don't have the stats, it becomes harder to match.
Listen carefully to the fields first year med students say they are currently interested in and compare that to match day. Many people change their interests and some aren't competitive so they apply to another field.