Yes there is a decline in incarceration rate in Federal and State prisons (for those with terms of 1 year or longer) for 2008-2018 (most of which is during Obama-Biden) which by itself should be lauded, but
1. BJS data does NOT include local and county jails for those with shorter terms than a year. The American Jail Association itself states that a bit less than 1/3 of the total incarcerated in 2009 were in local/county jails and estimates "a few hundred thousand" more in "lock-ups" https://www.americanjail.org/jail-statistics but also states that "no one knows the exact number". Sounds like China, Guatemala + other Latin American countries, the Gulag ... only worse. We have no clear idea what is going on in aggregate at the local level, with increasing bail, court fees, debtors prisons, increasing privatization of both jails and bail collection and increased local "law-enforcement". So the BJS "improvement" may well reflect just a shift and lesser accountability.
2. While the drop is good, the US incarceration rate is still 3-4 times that of other "developed" countries, as well as beating China both in rate by a factor >5X and in total number. So there was plenty of room to drop and there still is plenty of room to improve.
3. I don't know how much to credit Joebama, since the data does not indicate deviation from the trendline before 2008 or after 2016.
4. What jumps out from the BJS statistics is that compared to the rate for White people, the rate is still(!) >2X for LatinX people and >4X for Black people. White "fact checkers" and commenters tend not to discuss racial disparities, possibly because they are sooo progressive they "don't see race".
Typical white male fragility to distract from the main point the documentary is making about racial disparities and continuing forms of forced labour in the US.