Well, as I complained a lot / several times (here being one of the post, I add it here) about TrueOS downloading all packages all over again during update even if they are already current AND I just updated my two systems I can state the following:
As I suspected (but never tested / confirmed until now) TrueOS only downloads all packages all over again if the pkg-cache is empty or corrupted.
For the first time since a very long time I used SysAdm (instead of terminal) for the updates and also did not perform an in-place-update ("-static").
As it turned out, one system had all the files still in pkg-cache from last update, the other one did not.
So, the second system “had” to download about 2,4GB of packages of which only two were “needed” for the actual update. So it took hours to download while the actual update process only took seconds (and 1 or 2 minutes for creating a new BE etc.).
On the first system the downloading process was short because it only had to download those two packages. The update process was the same as on the second system.
So, not deleting the pkg-cache can save a lot (!) of time. I had to do it before because there was not enough disk space which isn’t an issue anymore.
That means, no more -static updates and unnecessary downloads for me anymore (for now) - hopefully.
Now, I love TrueOS a little bit more again…
P.S. …but I still haven’t figured out what those “x number of packages to be downloaded” messages mean, because only in case of FreeBSD base and maybe the TrueOS core that number seems to be correct. Sometimes it says maybe 150, and only 10 are downloaded, sometimes it says 1, and 10 are being downloaded, depending on the package (application).
And you never know at the beginning of the download / update process (if all packages have to be (re-)downloaded again) how many packages are to be downloaded alltogether because they are all separated “by subject” (e.g. TrueOS core, FreeBSD basis, any installed application (e.g. DE, browsers, java, whatever) - so (unless you did it a bunch of times and know all the packages you have installed) you get surprised that yet another package has to be downloaded, just when you thought now it should finally be done downloading and get to updating / installing - my most “favourite” one so far is “noto” (>= 800 MB)…