The paper blatantly lies about proving that if P=NP, then markets are efficient.
It actually argues that if P=NP, and Moore's law continues indefinitely, then eventually someone could build an efficient market.
If Moore's law continues indefinitely, then we will climb the 2^n NP problem cost with a 2^t computer speed, which means that any specific NP-hard problem will become solvable in an amount of time linear in n.
However the number of stock data points goes up over time, making it more like 2^(n*t) cost.