Yes, It applies to both Multiline (Text and Textbox) but for it to work you have to predefine its bounds especially Horizontal so that it won’t expand horizontally
Here you could see I have both Multiline Text and Multiline Textbox (One is for UI Text and other is for Player Input but could be Disabled through Read Only Option)
Here, I have used Horizontal Box with 0.5 and 0.5 Fill for both Multiline Text and Textbox and both of them Expand Vertically since they can’t expand Horizontally.
Also I am using Default Settings for both Multiline Text and Textbox.
Do note- It does not Apply to (“Text”), only Multiline Text or Multiline Textbox