The average-median thing seems to be just a mistake by whoever wrote that summary. If you look at the full report, this is what they have:
"Workers in the New York City tech ecosystem earn 49% more than the average City-wide hourly wage. The hourly wage for the tech ecosystem is $39.50, while the average City-wide wage is $26.50."
Your other points are valid, of course.
Edit: this is the full report and is quite a bit more informative than the summary: http://www.hraadvisors.com/wp-content/uploads/2014/03/NYC_Te...
Edit2: no longer completely sure what they are talking about:
"As of 2013, the average New York City median hourly
wage was $26.50. Tech ecosystem jobs pay above the
City-wide average. In fact, tech ecosystem workers are
paid 49% more than the City-wide average of $26.50.
In comparison to this average, tech workers in tech firms
earn 75% more, tech workers in non-tech firms earn
51% more, and non-tech workers in tech firms earn 25%
more."
I suspect their "average" "median" income is median income by job category averaged together. With that said, it looks like they arrived at the tech average wage in a similar fashion.