That is Pure Fiction, the 40 hour Work week came about as a Reaction to Train Accidents
It was found that People working 60 to 70 hours per week where not as Alert as 40.
So the U.S. Congress passed the 40 hour work week.

It happened before unions where well organized or had much influence, It also came about with out any Union advocy.

But I often hear Union Apologist try to take credit for it.

But lets Grant your Fiction, What has the Union done for the American Public in the Past 50 year?

I now work for a Non-Union Company, I get paid better, have better Health insurance, Better Retirement benefits and a Much better working condition than I did when I worked for a Company where I was FORCED to join the Union.

I also have better job security, for this company is doing well and values it’s Employees.

When I worked for the Union Company, the Union Reps would say things like you. “Oh, if it where not for the every one would be working 70 hour work weeks.
That Union members get paid better,. That you must Thank the Union for your Great Health Insurance…..It was all Lies.