On a quick search I couldn't find any sources to back it up, but I also couldn't find any to refute it.
Considering around 24,000,000 Soviets died during the war, it doesn't seem implausible, so how true is my friend's claim?
Not true.
For more information, see this answer by u/davepx, and this answer from yours truly.
The long and short is that maybe 63% of all Soviet males born in 1923 were dead by 1946. But out of this cohort of 3.4 million males born in 1923, only 700,000 or so had died in World War II. Another 800,000 had died in infancy, and a further 800,000 had died before age 18.