Default user.v5 not being delivered to domain users answer
I asked this question yesterday and have since found a possible answer. This site is SO secure I can't even comment on my own question, to let the 16 people following the question know that there is a fix. I haven't fully tested yet, as I'm waiting for replication to happen.
The answer is in this article about mandatory profiles. There is a chart with which v version applies to which Windows version. Default user.v5 is ONLY for Windows 10 versions 1507 and 1511. All other version of Windows 10 ( 1607, 1703, 1709, 1803, 1809, 1903 and 1909) use default user.v6.
I have a book (written by Microsoft MVP Jeremy Moscowitz) that was probably written before Microsoft made the change.