I can confirm that the file "share\themes\MS-Windows\gtk-2.0\gtkrc" is the same for both from portableapps.com and from inkscape.org for version 0.92.3.
I can confirm that the file "share\ themes\ MS-Windows\ gtk-2.0\ gtkrc" is the same for both from portableapps.com and from inkscape.org for version 0.92.3.