If I try to summon an item display and try to give it the scale 2.5, it doesn't work.

However if I try to give it the scale using /data merge it works.

 

Commands:

/summon minecraft:item_display ~ ~ ~ {transformation:

{scale:[2.5f,2.5f,2.5f]}

,item:{id:"minecraft:armor_stand",Count:1b,tag:

{CustomModelData:1}

}}

 

/data merge entity @e[type=minecraft:item_display,sort=nearest,limit=1] {transformation:

{scale:[2.5f,2.5f,2.5f]}

,item:{id:"minecraft:armor_stand",Count:1b,tag:

{CustomModelData:1}

}}