I was taught to slightly crack most chords (on harp) unless the notation indicated otherwise. I discovered this must be an American habit when our orchestra had a guest conductor from Europe several years ago who asked me to stop arpeggiating the chords. I didn’t know what he meant until I realized he didn’t want the chords cracked or rolled at all, just played flat. I don’t remember what the music was. I did what he wanted, but I didn’t like the sound of it.