If someone can work out when they are used i can update the strings

As I understand, It supposes to be used as Default Height and Default Width of the editor when no width and height is provided on editor form field type https://docs.joomla.org/Editor_form_field_type

However, due to a bug in the current code, that Width and Height is always use even the width and height provided in field definition (that bug should be fixed)

My comment is that it states

Only applies in Advanced and Extended mode.

We dont have those modes anymore.

I had a short look and I would say those parameters should be removed.
width and height are set in the editor form field with defaults: width= 100%, height=500 (px)
That is used in the article text edit.

Edit:
If a developer is using direct call he should fill the needed values
$editor->display('name'....

The values set in the plugin could be used as default in this case, but how do you explain this setting to the user?

Are 0 valid for width and height in some case? I would guess so and then you can't use any default in the display method.

#14835
#14033

If you really want to customize the values you can use a system plugin - method onBeforeRender()

Closed see #15059