The problem is, who gets to decide if a grievance is petty? IMHO, the person filing the grievance(any grievance) probably feels as justified as does anyone filing for something else and has the right to be heard at panel (or as far as it has to go) to get the matter settled. I agree that the filing for 10 minutes of a SUP working is pretty silly, but the person filing may think of it a different way that indeed makes sense to them. I have always thought of the grievance process as a kind of Umpire to decide on matters of difference of opinion of how the contract is interpreted and applied. Much of the language in the contracts is vague to the rank and file as well as management and it takes a challenge to gain clarification.
What I think is petty may well be, justifiably, a big issue to someone else.