Xfce4: screen visible upon resume before xscreensaver locks it

[Celejar <celejar@gmail.com>]

Hello,

I'm running Xfce4 on a recent install of Sid. I have configured Xfce4
to "Lock screen before sleep" (in Session and Startup / General), but
when I use xscreensaver, when resuming from suspend the screen is often
visible for a brief period before xscreensaver kicks in. I have not
seen this problem when using light-locker. I also tried briefly with
xfce4-screensaver and did not see the problem, but I have not done
extensive testing with xfce4-screensaver.

This is obviously a serious problem: I see that this has been a
commonly reported Xfce issue, with various distros / screensavers, etc.,
over the years, e.g.:

https://bugs.mageia.org/show_bug.cgi?id=28286
https://bugzilla.xfce.org/show_bug.cgi?id=14782
https://bugzilla.xfce.org/show_bug.cgi?id=15929
https://askubuntu.com/questions/1383379/xubuntu-desktop-visible-after-suspend-before-lock-screen

but I can't make out whether I have misconfigured something here, or
whether this is a serious security bug in the current Xfce4 -
xscreensaver integration.

Celejar