See where it's telling you to pull the link from?
Notice that it's
not the URL from the address bar?
compare these two URLs:
followed YT embed instructions
https://youtu.be/ScuwBnXgCv8 <----- embed works fine, no SWF download
didn't follow YT embed instructions, grabbed link from address bar
https://www.youtube.com/watch?v=ScuwBnXgCv8 <----- embed doesn't work, triggers SWF download b/c YouTube parser won't display it
I also experimented with "https" vs "http" and there appears to be no difference either way
I've tested this on a Mac, a Win7 machine, my Android phone, my Kindle Fire tablet, and an iPad mini and it seems to work the same in each case