Lighthizer in prior talks was demanding ability to verify implementation of reforms (e.g. Inspections) which China balked at allowing. The US is pushing hard to prevent China from gaming the talks/ negotiations. No longer is the US allowing promises at least in talks to date.
From a lawyer friend who is close to the discussions, "Even the doves are hawks now" in regards to engagement with China.
It is my opinion while not asked of me that brute force will be the only way to make China concede while capitalizing on their current economic weakness.
There is a naivety about China's ability to manage towards the long-term. Robert Lighthizer is leading the negotiations and isn't a neophyte in US China relations. He has taken a hard line with China expecting to re-balance the relationship. Thankfully, Trump has stay out of the way, but it is wrong to assume that China can wait this out.
China's economy is stalling and is over-leveraged. There is immense pressure on Xi from political rivals to strike a deal and prevent unrest due to the economic slow down. The tariffs and singular approach that Trump has taken actually works, but I'd argue that it was dumb luck on his part vs grand strategy.
Dube's paper is more in line with conventional economic thinking: On average, minimum-wage increases eliminated jobs paying below the new minimum, but added jobs paying at or above the new minimum. The two changes effectively cancel each other out.
There may be another factor lurking behind the apparently contradictory findings: Neither paper has gone all the way through peer review and been published in an academic journal.