Belts were and still are a new TSA obsession that started with the NoS. The "logic" behind belt removals applies to passengers going through the NoS, but it has turned into a 100% belt removal requirement at many stations regardless of whether a NoS is in play. Like most TSA obsessions, it gets worse over time and continues to lose whatever meaning it had at first.

I've been forced more than once to remove a belt (small buckle, never alarms) even when exempted from the NoS because I was carrying an infant. In one instance, the screener actually verbally went through his tortured thought process of telling me to remove the belt while he directed me toward the NoS, then realizing (and stating) I wasn't going through the NoS because of the baby, then telling me I had to remove the belt anyway (just because). You could almost see the guy's brain cell struggling to function.