It's doubtful that you'll get a positive, official assertion.
But, let's do some math. If they normall get 200 per week, and boys can go a year earlier, they could conceivably get an extra 52 weeks * 200/week = 10,000 applications. So 7,000 doesn't seem unrealistic. I know a number of boys and girls who were waiting to reach the appropriate age, and put in their papers as soon as that was announced.
At one point there were about 55,000 missionaries out at once, which would be in the ballpark of 500 applications/week, so 200/week seems completely plausible. If anything, the claimed 200/week may be low, which would make the "surge" of 7,000 applications even more realistic.