This topic interests me because my company uses this to punish pilots. Our reserve is a strict "90 minutes to the parking lot" and 10 minute call return. They manage to hand out several no-shows a month due to pilots literally calling scheduling back at 11+ minutes for a reserve call or showing late. Unfortunately there's little appetite to spend negotiating capital to fix this because the majority of pilots have no chance of sitting reserve unless they pick up a shift and they see reserve staffing as cannon fodder to make sure they make it home on time that night (rescue flights, minimal delays due to sick calls, etc). So be glad your show times are undefined because if it becomes specific, yes the company will have no choice but to enforce it. Also if people abuse the vague report time you will lose it because at the end of the day, unions know where the majority is and they will say they had no choice because the company made it too expensive to keep.