“[x] Reset field positions” resets only the positions of the fields selected in the “Fields to Update” box, which does make sense to me.
However, if you select the “Reference” or “Value” fields, then their contents always gets reset too, while the value of the Footprint link only gets reset with the checkbox: “[x] Reset fields which are empty in library”
This looks like a bug or forgotten feature to me.
A logical solution to me would be to make an extra checkbox in the options part to reset the value text.
It is also an old dialog. It was from before Eeschema / Tools / Edit Symbol Fields, which gives you a lot of control over the contents of all fields, but not attributes such as location and text size.
There is also a function I forgot how to activate. There is a function to make all hidden fields of all symbols visible, but I can’t find it anymore.
I doubt that there will be much interest in changing this for KiCad V5.1 while KiCad V6 is “just around the corner”.
In KiCad V5.99 Eeschema / Edit / Change Symbols has similar but extended functionality and looks quite differently:
KiCad V5.99 also has Eeschema / Edit / Edit Text and Graphics Properties, similar to Pcbnew V5.1.8.
I could not get it to “work” in KiCad V5.99 at all. Apparently the “Change Symbols” always works with the filters in the top of the dialog, and never globally with all symbols.
Fixed typo (2x) “File” -> “Edit”.