Scintilla and Lexilla are compiled into Geany, Geany does not link against them. So other than development versions in Git there is a one to one relationship between Geany version and Scintilla/Lexilla versions. So I'm not sure adding more to the debug output would add much value.
If there was a need for this the `update-scintilla.sh` script could use the `version.txt` file contents to edit a string to be displayed when an update happened, not at configure time.