most groups have a length of recovery requirement prior to leading a meeting. I am not too sure about the content of your other questions- Are you asking why speakers tend to announce their time in recovery?
i do so because when i am listening to a speaker i kinda like to know the context of the ESH. makes a difference to me if it was a decade vs a week of recovery...
BTW- never had anyone in NA tell me i needed to 'qualify' myself ....?