In the olden days, if one filed a code-level support ticket and the issue turned out to be a bug in Apple software, one wouldn't necessarily get charged for the support request. Is this still the case? What is the determination for whether a ticket is expended or not – or does it come down to the support engineer's discretion?
I don't speak for Apple but from my experience I usually get credited back the ticket if they think the issue I'm reporting is a system bug initially (before talking to an Apple engineer) and they don't think there is a workaround they can advise.
For example I opened a TSI recently and I got an email "No workaround is available" and I got my TSI credited back.
Sometimes they won't necessarily think your issue relates to a system bug but then after talking to an engineer they may realize it is. In these cases I don't think they will refund your ticket once you start communication with an engineer (but I'm just speaking on my own experience I have no idea what their official policy is). They may suggest a workaround in these cases (but may not have one to offer either). Then everything ends with you filing a Bug Report and you wait but in my experience none of my bugs ever got fixed and I never hear from them again.