@norb I really enjoyed this collection too, and know what you mean about how modern a lot of it seems. Hemingway had a very publicly macho persona, and so when I first read him it was a little bit at arm's length expecting some of that to bleed through. I was really surprised by his actual writing about masculinity though, though I can't tell how much that is me as a reader colouring what I read with my own biases.
I definitely had this sense, especially with bull fighting (which he is absolutely obsessed with), that he was really interested in the performative aspect of masculinity, and he has so many characters who act in brash and stupid ways that cost them dearly (often with their lives) just to prove themselves as fearless or manly to other people, often other men. Two that spring to mind are the story about the man and his wife on safari whose wife covets the big-game hunter guide with them after her husband ran from the lion. This then drives him to overcompensate when they see another lion, in order to restore his wife's respect (though it's implied it was perhaps already gone), and he gets himself killed. The other one, was one of the really brief interludes, about two spanish boys, one of whom tells the other he is not afraid of bulls. To prove this to his friend, he asks him to tie knives to the legs of a chair and then come at him. It ends with him getting gored and bleeding out. These two really stuck with me long after reading, as they just seemed so different to the public image of Hemmingway in how critical they seem to be of the macho expectation of fearlessness.
The story that really, really stood out to me though was Up In Michigan about the girl who day dreams about the farm hand coming back from the hunting trip and then it ends with her fantasy evaporating as he shows interest in her, but with far more forcefully than she had hoped for, and it ends in her being assaulted by him. There was something in the austerity of the language but how evocative it is in the depicition of having a crush, and how heartbreaking the ending is, that really struck me. He also absolutely represented the traditional, forceful masculinity of the love interest as a destructive and harmful thing which caused both deeply physical and emotion pain to the protagonist.
The collection really flipped my third-hand inherited perception of Hemmingway on its head. I really enjoyed most of it.