To give a sense how much benefits code and tax code have in common, see this worksheet for SNAP eligibility, which resembles a second tax return: https://www.fns.usda.gov/snap/recipient/eligibility. You get to do something similar, again(!), for Medicaid.
The American benefits code is a patchwork of conflicting sensibilities of the electorate: the smallest possible tax, paternalism and suspicion against the poor, plus a few policy analysis trying to obtain the maximum poverty reduction within those constraints. The result is a thicket of means tested programs with extremely steep phase-outs and a lot of paperwork. The all-in EMTR for an American with income between 0-40K a year is chaotic beyond reason as a result as they roll up the income spectrum.
This person who gave the presentation is indeed in one of the worst cases for the code: a single parent with multiple children.