When summoning an item_display entity, the default/omitted item_display property is fixed, rather than none as listed in the 23w06a article. Also, none seems to display transformations for fixed, and fixed displays the transformations for none.

commands used, from left to right:

/execute align xyz run summon minecraft:item_display ~.5 ~.5 ~.5 {item: {id: "minecraft:diamond_sword", Count: 1b, tag: {Enchantments: [{}]}}}

/execute align xyz run summon minecraft:item_display ~.5 ~.5 ~.5 {item: {id: "minecraft:diamond_sword", Count: 1b, tag: {Enchantments: [{}],item_display:"none"}}}

/execute align xyz run summon minecraft:item_display ~.5 ~.5 ~.5 {item: {id: "minecraft:diamond_sword", Count: 1b, tag: {Enchantments: [{}],item_display:"fixed"}}}

With a custom item model that has the fixed field configured in its .json file:

Also, the property item_display should be probably changed to something else to reduce confusion, like display_mode