If you watch the video you can see what appears to be a hard reset occurring on the receiver and not a handshake takeover. This looks more like a "crashing" device.
I suppose if the model was high enough control could be established after a reset but rather doubtful.
I don't think one can dismiss this along the lines of " well everything out there can be hacked" and even though a device like this would never get current FCC approval that still wouldn't stop someone from building/buying/using one.
Probably Spektrum can add some encryption to prevent this from working but it may not be as simple as a firmware upgrade considering a lot of receivers can't be upgraded.
https://www.youtube.com/watch?v=abl6oOxLRXs&feature=youtu.be