If, for example, 2 and 3 are in the same map grid, only 2 will give you the grid, and 3 will keep silent.
Suggested solution is to make the 3 say something along the line of "I'm alive". If not, making him repeat the same grid coordinates as the one 2 said 1 second before, just like Arma 2 and before, is better than saying nothing.
This used to be the way it worked in A2, but then I believe it was changed in an update. I think the reasoning was that most of the time if you're separated from your squad, they're most likely all together and so only one AI giving a position is sufficent. And if you want an individual report you can always just select individual squad members.
Before the change, every unit would spam the radio channel with the same information and it would be annoying. However I agree that the other team members should give a quick response, even if it's just "moving" or "ready".