Replacement header not working

I am having an issue where a replacement header isn’t replacing:

Section 2 - Media Options When None Used (for Glulx only) (in place of Section 3 - menu art and music (for Glulx only) in StartEnd MenuPages by ShadowChaser)

To display_start_art: do nothing.
To display_end_art:  do nothing.
To play_start_music: do nothing.
To play_end_music: do nothing.	

Code in the extension:

Section 3 - menu art and music (for Glulx only)

Include Glulx Image Centering by Emily Short. 
Figure openingFigure is the file "startpicture.jpg".
To display_start_art: 	display figure openingFigure centered.

Figure closingFigure is the file "endpicture.jpg".
To display_end_art: 	display figure closingFigure centered.

Sound of startingMusic is the file "startmusic.ogg".
To play_start_music: 	play the sound of startingMusic.

Sound of endingMusic is the file "endmusic.ogg".
To play_end_music: 	play the sound of endingMusic.

I’ve tried fiddling with the wording, moving the (for Glulx only) around or removing it, but no luck. This just isn’t replacing the header. I’m trying not to edit external extensions if at all possible, but I can’t figure this one out. I have other replacement headers that are working fine.

I don’t mean to single out this extension as a question about this extension or for the author, as I have no reason to believe it is this extension that is causing the issue (but then again I have no idea what is causing the issue). I assume this is just a syntax error in my replacement header I am not seeing on my end or something?

Try removing both of your (for Glulx only) specifiers. (Not just the one in the parentheses, the one after the header name as well.)

Removing the one in the in place of parenthesis results in the compiler not finding the matching header in the original. It seems it considers “(for Glulx only)” a part of the header name. Is this a bug? I guess I can just edit my copy of the extension, but I was just trying to avoid that 100% if at all possible as a matter of course.

This works when I try a simplified example:

Test Extension by Andrew Plotkin begins here.

Section - Alpha

When play begins:
	say "Alpha."

Section - Beta (for Glulx only)

When play begins:
	say "Beta."

Test Extension ends here.
Include Test Extension by Andrew Plotkin.

The Kitchen is a room.

Section - Alt-Beta (for Glulx only) (in place of Section - Beta (for Glulx only) in Test Extension by Andrew Plotkin)

When play begins:
	say "Alt-Beta."

I tried:

Section - Alpha (for Glulx only) (in place of Section 3 - menu art and music (for Glulx only) in StartEnd MenuPages by ShadowChaser)

To display_start_art: do nothing.
To display_end_art:  do nothing.
To play_start_music: do nothing.
To play_end_music: do nothing.

and this:

Section - Alpha (in place of Section 3 - menu art and music (for Glulx only) in StartEnd MenuPages by ShadowChaser)

To display_start_art: do nothing.
To display_end_art:  do nothing.
To play_start_music: do nothing.
To play_end_music: do nothing.

Both compile fine in the IDE to run in the in-editor game results, but it’s during Release or Release for Testing that it has an issue. It says that Figure openingFigure is the file “startpicture.jpg” doesn’t exist… but that’s the whole reason I’m trying to do the replacement.