Specifically, it appears they didn't really do any research into what caused the Penn Railroad collapse, which was not caused by high interest rates but instead by a combination of actions which would be considered fraud today (due to conflicts of interest that would never be allowed and exceptions to financial reporting in the rail legislation).
They basically couldn't raise prices due to regulation, and no bank would loan to them. The one bank that would loan to them required they have seats on the board of directors. They loaned money at high interest rates, bought up the senior bonds with the interest payments, took control of the board, loaned money to themselves (effectively), paying dividends out of debt, and then forced bankruptcy and let it all collapse in the hope of a government bailout (which they got because rail is critical to food security and energy).
It also neglects stagflation but does mention Volcker, drawing the wrong conclusions of what really happened, doesn't mention the S&L debacle aside from a brief mention (which was huge as well), neglected the whipsaw effect.
The biggest problem I have with it, is it neglects a lot of important factors and only focuses on policy which doesn't match up with reality and largely only what fits their narrative if you didn't know better. There was also no mention of taking the currency off the gold standard in 1971. Most importantly, they don't use any of the M2 or velocity of money data. Its available from the Fed website but it doesn't support much of what they said, and shows how expansion of the money supply drives inflation in cost push or demand pull inflation.
MMT suffers from major problems. The people that subscribe to it largely only see these large sums in a very narrow context which leads to poor conclusions, and an idea that you can print money continuously into the future with no consequence. It largely was what led to quantitative easing (or money printing).
Graeber has a great book on Debt, which goes into the historical examples of what happens when you debase currency like this (no matter what you call it), and there's some very interesting research in how the Economic Calculation Problem related effects can be seen as rational pricing and price discovery fail in markets denominated in unbacked fiat. The latter being most commonly known for its historic roots as an intractable problem with non-market socialist systems where the means of production are held by a single entity. The debate/problem still isn't solved 100 years later.
Additionally, the people making policy can't control what people choose to buy and sell goods at. Inevitably you get shortages when they try, business sectors concentrate, points of failures are introduced, and people leave the business when its not profitable. Then you get things like the baby formula crisis where the only factory remaining is shut down for safety reasons (as a result of cost cutting) and no one can get baby food in Florida. Once sector concentration reaches a certain point, its a short step away from nationalization in furtherance of solving the shortages through greater regulation.
Needless to say it doesn't work, and I'd expect at least some of that to be addressed, but it wasn't. What's covered seems misleading, and very much divorced from the reality.