Re: “Sacra Propediem,” you’re talking about 1921 fashions and dances.
And frankly, if you have ever seen footage from 1921 nightclubs that were considered hinky in the US, sometimes women did wear stuff that most people today would never wear, and dance with their lack of underwear obvious while they did high kicks. And it was worse in Europe. And sometimes they did go try to church in that stuff in Italy.
The wilder flappers also weren’t wearing corsets or bras, for the most part, so the top half was ridiculously obvious under their clothes. And women weren’t just wearing rouge on their knees, so it was really really obvious that they weren’t wearing bras. I don’t need to go into more detail, do I? Because there was a lot of this stuff, honestly.
But you also notice that Pope Benedict XV did not define what was modest and what was not; he just said his piece and asked people to do better. He didn’t give sleeve lengths or bodice heights, because those change.
As for shirtless men – on the day when XY-chromosome men can nurse babies with their tiny little nipples, and develop entire secondary erogenous zones and nerve systems on their flat little chests, that’s the day when I’ll worry about men being too immodest with their shirts off.
Given all the wicking undershirts and shirts that we have now, and all the worries about skin cancer, I doubt we’ll see bare male chests much longer.