Hi, devil's advocate here. If a TL takes an extra 15 minutes and they are scheduled for 40 hours, they will have to cut that time later in the week to avoid overtime. Your GSTL could stay an extra 4 hours without adding any payroll because he/she would just leave early a different day. They do need to be responsible with it because you don't want to cut time on a Saturday, but it does not affect payroll in the way that another TM would by staying just a couple minutes.
ETLs aren't paid hourly. Standing around doesn't add payroll because theoretically they could stay late to finish up. Also, they generally work 10 hour shifts and they don't get scheduled breaks the way that we do, so they need some time to breathe. Some ETLs don't work hard and will take advantage of this, but in a lot of cases team members see the ETLs when they sit in their offices for 30 minutes and didn't see the 8 consecutive hours of work that preceeded it. Having said that, any half decent STL should make sure the ETLs stay productive. And the DTL should be all over the STL's ass if the store isn't doing well.
Whether you make sales or not, payroll is going to be shit. Absolute shit. A green sales floor isn't profitable. Success isn't profitable, but mediocrity is. There is a point at which adding $1000 of payroll doesn't result in a sales increase of $1000. Target is somewhere around that point now (and we can all argue whether or not they dipped too far below it, but the truth is that we can't really know).