New Document Master does not use default template

I’m running on Version: 24.2.7.2 (X86_64) / LibreOffice Community
Build ID: 420(Build:2)
CPU threads: 16; OS: Linux 6.8; UI render: default; VCL: kf5 (cairo+xcb)
Locale: en-US (en_US.UTF-8); UI: en-US
Ubuntu package version: 4:24.2.7-0ubuntu0.24.04.4

I start LibreOffice from the start menu. It comes up with the template I marked as default. Then I click on File->New->Master Document.

It does not come up with my default template which is used by all the documents to be included.

I can click on the Styles drop down and “Load Styles from Template”,
select my default template and click all the boxes to get the right template.

What template is the Document Master using? Can I modify it?

The Writer Guide has a little chapter

Creating a master document template

A master document template is created in much the same way as any other template, described in Chapter 10, Working with Templates:
  1. First, create the master document using File > Send > Create Master Document, as
    described in earlier sections of this chapter.
  2. Then, use File > Templates > Save as Template to create the template (.otm), which will then be listed in the Templates dialog along with other templates.
    Tip
    Include in the name you give a master document template some indication that it is
    not an ordinary template.

Well, that does not look like re-using an existing template.

I don’t know, but the above description shows how to build your own.