Review D28062 of /usr/src/UPDATING with regard to upgrading FreeBSD and inconsistency with the FreeBSD Handbook

[Graham Perrin]

1)

<https://reviews.freebsd.org/D28062#change-5KzY5tEtVUor> lines 2273 and 2275

With ZFS in the mix, /usr/src is present but empty (the file system is 
not mounted).

If single user mode is recommended, then why is this not in the FreeBSD 
Handbook? 
<https://cgit.freebsd.org/doc/tree/documentation/content/en/books/handbook/cutting-edge/_index.adoc?id=84d56d3868a699c64c51d7453cedab0f3468ba03#n620>

2)

<https://reviews.freebsd.org/D28062#change-5KzY5tEtVUor> line 2274

etcupdate -p

I get:

 > No previous tree to compare against, a sane comparison is not possible.

<https://photos.app.goo.gl/3a64FfsNkGUTPj1XA>

In the past I simply ran etcupdate after make installworld.

If etcupdate -p fails before make installworld, then should the 
subsequent etcupdate be with or without option -B ?