interesting video
it's strange because it seems you know it but I tell you anyway: fyi Flatland is the name of that BMX discipline these 2 flatlanders showed you. Flatstyle is the name of the initiative/website of Jim MacKay for longtime apparently, it's not a sport as you wrote it in that youtube description.
And to know very interesting and very good editing work, check Bobby Carter's work through his Diversion videos serie for example