I agree.
I have friends who wear makeup to work that reason. The confidence from looking like they are put-together. I imagine wearing a suit can be the same mental confidence.
Most certainly the put together effect cannot be understated. I looked up the definition of confidence one day and fundamentally it means holding onto some intimate knowledge like a secret that provides an advantage to the holder. It has grown to mean so wany things it's one of those words like 'agile' where agreement on terminology ironically masks disagreement on ultimate meaning.