It is, but so are self-reported industry salaries. This isn't perfect data, but it is (fairly) reliable data that all comes from one place.
Source: I am one of the two people behind the site and for my two H-1B visas the maximum salary that was reported for my visa was what I got paid.
Do they still do that? I'm guessing no since you didn't use it.
http://www.h1bwage.com/item.php?q=3277027
In this example, the wage rate is $106,600, while your site report, I believe, the max rate of $193,400. I was shocked for a moment to see a data scientist making almost $200K!