Avi – the shirts you’re referring to are probably undershirts.
Piskei teshuvos isn’t a source; it’s a compilation of sources, so would you mind posting which source he brings? Also, if shirts and pants aren’t required to not be freshly laundered, then that just leaves…suits? Clothing that is meant to protect against sweat, like socks, underwear and undershirts, are not a problem because they’re not worn for their own sake, nor are they “choshuv”, but pants and regular shirts? They most definitely are.