"Line walks" are an absolute joke. It made sense back when the production supervisors actually managed and oversaw metrics...
Quite frankly, a supervisor now serves as a misinformed person reporting on something his/her area manager or superintendent hasn't taken the time to explain. There's so much going on in the backend, but the true issue is poor communication between Area/Superintendent/Operations/GM and the production team leadership (Production Supervisors/Team Leads).
These line walks often happen with executives and reps from customers like Rolls Royce, Airbus, etc. present and production supervisors aren't armed with the necessary training/education that is required to speak fluently on metrics that they really don't have much influence on.
The supervisor essentially serves as a cheerleader to their team and/or shields them when targets aren't met and leadership wants you to light a fire under their bee-hind for poor performance. Again, a lot of times... this is a planning issue that almost never has anything to do with individual performance of production workers.