proper config for specific pks upgrade from stable to testing

[daggs <daggs@gmx.com>]

Greetings,

I want to upgrade these specific pkgs from stable to testing:
libvirt-clients/stable,now 5.0.0-4+deb10u1 amd64 [installed,upgradable to: 6.4.0-2]
libvirt-daemon-system/stable,now 5.0.0-4+deb10u1 amd64 [installed,upgradable to: 6.4.0-2]
libvirt-daemon/stable,now 5.0.0-4+deb10u1 amd64 [installed,upgradable to: 6.4.0-2]
libvirt0/stable,now 5.0.0-4+deb10u1 amd64 [installed,upgradable to: 6.4.0-2]
qemu-kvm/stable,now 1:3.1+dfsg-8+deb10u6 amd64 [installed,upgradable to: 1:5.0-6]

so I've updated my files as such:
# cat /etc/apt/preferences
Package: qemu-kvm
Pin: release o=Debian,a=testing
Pin-Priority: 900

Package: libvirt-clients
Pin: release o=Debian,a=testing
Pin-Priority: 900

Package: libvirt-daemon-system
Pin: release o=Debian,a=testing
Pin-Priority: 900

Package: libvirt-daemon
Pin: release o=Debian,a=testing
Pin-Priority: 900

Package: libvirt0
Pin: release o=Debian,a=testing
Pin-Priority: 900

# cat /etc/apt/sources.list
deb http://security.debian.org/debian-security buster/updates main
deb-src http://security.debian.org/debian-security buster/updates main
deb http://deb.debian.org/debian/ buster-updates main
deb-src http://deb.debian.org/debian/ buster-updates main
deb http://deb.debian.org/debian/ buster-backports main
deb-src http://deb.debian.org/debian/ buster-backports main
deb http://deb.debian.org/debian/ buster main non-free
deb-src http://deb.debian.org/debian/ buster main non-free
deb http://deb.debian.org/debian/ testing-updates main
deb http://deb.debian.org/debian/ testing main non-free
deb http://security.debian.org/debian-security testing-security main

but when I issue upt-get upgrade, it looks like apt tries to upgrade unrelated pkgs like lsb-release, lsof and grub.
is that expected?
I want to upgrade only these pkgs + it's deps.
what am I doing wrong?

Thanks,

Dagg.