Hi, @nyx_fr (XIBE) 
(Usual disclaimer: please note that I'm just another Forum user here, I'm NOT an Ubuntu Developer and/or Ubuntu MATE Developer).
You've asked:
In April 2022, there was the following related discussion started by @JokerGermany regarding Ubuntu MATE 22.04 LTS ("Jammy Jellyfish"):
In that discussion, @franksmcb (Bill) started by replying the following:
... and then he added the following explanation:
... where he mentioned the following Bug in Launchpad:
"Bug #1706770 “Lock screen can be bypassed when auto-login is enabled” : Bugs : mate-session-manager package : Ubuntu" - https://bugs.launchpad.net/ubuntu/+source/mate-session-manager/+bug/1706770
That bug eventually lead @Wimpy (Martin Wimpress - one of the two Founders of Ubuntu MATE - "Team | Ubuntu MATE") to remove the "gnome-system-tools" software package from Ubuntu MATE, as can be seen in the following 2 comments in that Bug:
When Ubuntu MATE 22.10 ("Kinetic Kudu") was released, the following related paragraph appeared in the "Ubuntu MATE 22.10 Release Notes" - https://ubuntu-mate.org/blog/ubuntu-mate-kinetic-kudu-release-notes/:
"(...) MATE User Manager
A new utility, User Manager, has been added to complement the suite of MATE tools. User Manager replaces the aging
gnome-system-toolswhich was removed from Ubuntu MATE in the 22.04 release and allows you to add/modify/remove user accounts. It also includes the ability to define which users are Administrators, enable/disable auto-login, set profile images and manage group memberships.
I hope this helps in clearing things up