Wouldn’t that count as slave labour?
Not according to the Allies at the Yalta conference.
By the late 1940s, the only people claiming that the labor enjoyed by the Soviets at the hands of captured Nazis was “slavery” - were Nazis.
By all allied accounts, using German labor to pay reparations was deemed acceptable given how the Soviets had just sacrificed 27 million people.
https://en.m.wikipedia.org/wiki/Forced_labor_of_Germans_after_World_War_II
They also claimed 7 out of every 10 Nazis killed in WWII, and by all accounts at the time, contributed the most to winning the war.