package-initialize warning despite no package-initialize

[Stephen Berman]

I just updated and rebuilt emacs from master for the first time since
the changes involving package-initialize in 24acb31c04 and 2db57579b0.
On restarting emacs with my initializations I got the warning "Warning
(package): Unnecessary call to ‘package-initialize’ in init file", since
I still had `(package-initialize)' in my init file.  Following the
advice in the doc string of package-initialize I removed that sexp and
restarted emacs, but still get the warning.  I do not have an early init
file and I rebuilt with `make bootstrap'.  I grepped for
package-initialize and found no calls to it in files in my load-path
other than startup.el.  Is the doc string wrong or is there something
else causing that warning that I've overlooked?  In any case, how do I
get rid of this warning?

Another surprising thing is that, although emacs-26 does not have the
above changes and hence AFIU should still need `(package-initialize)' in
the init file, yet starting emacs-26 with the same init file lacking
this sexp, my packages nevertheless are immediately available (I infer
this because my init file calls `pdf-tools-install' from the pdf-tools
package and viewing PDF files does indeed use this package in emacs-26
just as in emacs from master).  That is, it seems that
package-initialize is not needed in the init file in emacs-26 either, or
have I misunderstood this too?

Steve Berman