Hi @vkareh,
Is there a way to force a full rebuild? I scanned thru the Makefile, but I don't see anything I recognize as a flag to force that. Could you give me the command format to make that happen?
All I'm getting are messages like these:
make[2]: Entering directory '/DB001_F2/home/Downloads/MateThemes/mate-themes-3.22.26/desktop-themes/BlackMATE-border'
Making all in metacity-1
make[3]: Entering directory '/DB001_F2/home/Downloads/MateThemes/mate-themes-3.22.26/desktop-themes/BlackMATE-border/metacity-1'
make[3]: Nothing to be done for 'all'.
make[3]: Leaving directory '/DB001_F2/home/Downloads/MateThemes/mate-themes-3.22.26/desktop-themes/BlackMATE-border/metacity-1'
make[3]: Entering directory '/DB001_F2/home/Downloads/MateThemes/mate-themes-3.22.26/desktop-themes/BlackMATE-border'
make[3]: Nothing to be done for 'all-am'.
make[3]: Leaving directory '/DB001_F2/home/Downloads/MateThemes/mate-themes-3.22.26/desktop-themes/BlackMATE-border'
make[2]: Leaving directory '/DB001_F2/home/Downloads/MateThemes/mate-themes-3.22.26/desktop-themes/BlackMATE-border'
------- edit --------
And I just now understood what you meant, about only for maximized windows. I can confirm that behaviour as observed. My darker image is used for the maximized condition.
As a comment, that seems a bit of a restrictive (and not-helpful) pre-condition. 
------- edit 2 --------
I made the following changes,
root@OasisMega1:/DB001_F2/home/Downloads/MateThemes/mate-themes-3.22.26/desktop-themes/BlackMATE-border/metacity-1# diff metacity-theme-3.DISTRO.xml metacity-theme-3.xml
208a209,220
> <!-- START of innsert -->
>
> <draw_ops name="rounded_titlebar_unfocused">
> <include name="titlebar_fill_unfocused" />
> </draw_ops>
>
> <draw_ops name="rounded_titlebar_unfocused_alt2">
> <include name="titlebar_fill_unfocused_alt2" />
> </draw_ops>
>
> <!-- END of innsert -->
>
967a980,981
> <piece position="titlebar" draw_ops="titlebar_fill_unfocused" />
> <!--
968a983
> -->
root@OasisMega1:/DB001_F2/home/Downloads/MateThemes/mate-themes-3.22.26/desktop-themes/BlackMATE-border/metacity-1#
and "rebuilt" the MATE Themes, and the BlackMATE-border does show the darker titlebar for non-maximized windows. 
--------- edit 3 -----------
Issue submitted on GitHub, asking to update the Theme as per the observed oversight.
--- metacity-theme-3.DISTRO.xml 2024-04-08 20:41:47.000000000 -0400
+++ metacity-theme-3.xml 2024-08-16 16:33:40.363183333 -0400
@@ -206,6 +206,18 @@
<include name="titlebar_fill_focused_alt" />
</draw_ops>
+<!-- START of insert -->
+
+<draw_ops name="rounded_titlebar_unfocused">
+ <include name="titlebar_fill_unfocused" />
+</draw_ops>
+
+<draw_ops name="rounded_titlebar_unfocused_alt2">
+ <include name="titlebar_fill_unfocused_alt2" />
+</draw_ops>
+
+<!-- END of insert -->
+
<draw_ops name="border_focused">
<rectangle color="C_border_focused" x="0" y="0" width="width-1" height="height-1" filled="false" />
</draw_ops>
@@ -965,7 +977,10 @@
<frame_style name="normal_unfocused" geometry="normal_unfocused">
<piece position="entire_background" draw_ops="entire_background_unfocused" />
+ <piece position="titlebar" draw_ops="titlebar_fill_unfocused" />
+<!--
<piece position="titlebar" draw_ops="rounded_titlebar_focused" />
+-->
<piece position="title" draw_ops="title_unfocused" />
<piece position="overlay" draw_ops="rounded_border_unfocused" />
<button function="close" state="normal" draw_ops="close_unfocused"/>
---------- edit 4 ---------
Bug report #2077202 submitted on launchpad.