I do assume they are going to turn away guests in pajamas, underwear, g-strings, Vegas showgirl costumes or just nude, even though it doesn't specifically say those are prohibited.
But they will let you in if you show up in shorts, a tee shirt and tennis shoes, as long as none of it is torn and your tee shirt isn't considered offensive.
The only place I've seen a bunch of Disney guests in pajamas (excepting little kids of course) are the club level lounges.