Why is turnout percentage the metric you think matters?
We don't have 2016, but we could use one of his favorite sources, TargetSmart, and see numbers for 2020 and 2022. According to that, the difference in 2020 was 12.2% (58.4% - 70.6%) for the final vote. In 2022 it was similar at 12.8% (43.7% - 56.5%).
One thing to know, Georgia is a bit tricky about voters roll and what it uses as turnout percentage. It is comparing "active" voters, which is actually a significantly smaller number than registered voters.
https://www.11alive.com/article/news/politics/elections/how-many-registered-voters-in-georgia/85-09aed09a-c375-4b6a-8618-62a34ba07d5b
For instance, in 2022, Georgia has 7,007,154 "active voters" but probably closer to 7.9 million registered voters. The TargetSmart numbers are using an estimate for registered voters. The Georgia Secretary of State data is all based upon "active" voters.
Based on the numbers from Election Data Hub, Georgia today has:
3,574,436 active white voters (2,251,895 / .63) [turnout divided by turnout %]
2,054,386 active black voters (1,021,030 / .497) [turnout divided by turnout %]
Georgia's Active Voters Report provides data as of December 2021 (https://sos.ga.gov/georgia-active-voters-report), which shows:
3,716,904 active white voters
2,058,705 active black voters
Based on that, there are 142,468 fewer active white voters now than in 2021, a 3.8% decrease. And there are 4,319 fewer active black voters, a .2% decrease. Because active white voters decreased more, each white vote is going to count more in terms of turnout percentage (as used by Georgia with "active voters"). If you were to compare the current votes with the 2021 active voter numbers, the turnout difference becomes less stark and compares favorably with 2020 and 2022 at 11%. (60.5 - 49.5)
Finally, I'll note that the Election Data Hub numbers are somewhat suspect. For instance, the top line number currently reports 4,017,718 votes, 7,242,975 active voters, for a 55.5% turnout (that math checks out). However, if you add up all the votes for each race (or each gender), the total numbers of votes is only 3.8 million. I'm not sure if the topline is updated separately from the breakouts or if the whole thing is generally broken.