I don't know the reason, Im not a coder.
This works fine on my custom Vb3.8.11 :
AdminCP / Styles & Templates /Add New Replacement Variable for each icon (size, appareance...) for each style (use the source code of the editor template as a guideline to replace the variables).
--------------- Added [DATE]1565977704[/DATE] at [TIME]1565977704[/TIME] ---------------
Example (change the size only):