[Simon Ubsdell] “If I have 5000 customers rather than 50, I have 100 times more revenue to service their support requests – and so on. There never comes a point of which volume of sales doesn’t entitle the user to the same level of support. “
My own guess is the likelihood of a response from Apple is relative to the potential uniqueness of the bug at the time you report it. While I’ve never received a response for an FCPX bug report I did for FCP Legacy and, in addition to emails, it resulted in phone calls and even an NDA.
If you’re one of hundreds or thousands they may not have anything to say beyond working on the fix.
If you hit on something rarely reported that they may need your help in verifying they’d be highly motivated to contact you.
A developer with a much smaller user base may not know how widely spread an issue is so they may be much more motivated to contact the user for verification.