That sounds like something that'd be true for every field, not just math. The nature of anything that's cutting edge means very few people will have looked at it yet let alone actually understood it.
I agree that the number of people that can understand a cutting-edge paper will be low. But, in CS for example, the number will be much higher than 100. I would assume that it would be in the 1000's worldwide. Since, it isn't my field I could speculate that cutting-edge biology would be understood by a lot more than 100 persons.