here's a topic of great concern run on fb and hf recently that has me miffed about how ignorant a lot of people who fly rc helis are. This is the topic on hf you should take a look at and consider, https://www.helifreak.com/showthread.php?t=792519.
Now why something like this is so close to home in some respect is that I've actually experienced a similar impact while flying only in the simulator, however repeated a half dozen times before I begun to counter react differently and also NEVER FLY CLOSE to me. I also NEVER FLY THE HELI OVERHEAD at close range. There were times when my eyes could not make out the orientation similar to the one who was hit and the heli ended up smashing into me in the sim, thankfully only the sim during wild no brain freestyle 3d (finger reactions only and heli goes where it goes, just keep it off the ground).
Now, you question how it could be survivable? depends on what part of the blade you are hit with and if you hit a main artery. When Roman was hit he was also hit with a heli speeding at 100mph, add in the rotary speed of the blades and you have quite a swing. He was also probably hit with the tip carrying the maximum speed and impact force due to the 25gr ballast within the blades remaining 100mm of tip.
When you calculate rpm it will be the same along all sections of the blade from tip to root but when you reduce the circumference the inner portion of the blade decreases in speed due to the shorter distance it covers in the same rpm, therefore the blade will not be exerting the same amount of momentum at the tip compared to the root or half a blade out (effectively half the distance = half the mph).
If I was able to reply to the hf topic I would have advised anyone flying in dark skies on a regular basis get some colored orientation led's and point some up, down, sides, and nose/tail. Don't use the spot beam ones but the frosted type. I've flown a rc heli at night with nav lights at night and it can be done but takes some getting used to.
I know what it's like to ditch a heli and the disgusting sound it makes when hitting an object or the ground, had to ditch a 450 when I flew across the sun and was temporarily blinded, brace yourself.
That guy had the heli only knife edge after a flip to upright so he thought and added cp rsu thereby into himself. He made the dangerous mistake of doing flips 90° in front of him like shoveling, other people over the years have warned of not flying toward yourself, not flying flips at 90° to yourself, not flying behind yourself neither over yourself and a few other proximity warnings for good plain old sensible self preservation concerns.
Why should I care? I've flown on a dark evening with snow and everything was dark and grey, the heli had no canopy and I was fifty feet out doing flips and rolls, inverted a little, getting snow in my eyes, but only with a 450 (which to some might be more challenging than a larger heli). leds were visible from the gyro, esc, and a small video cam on the nose so at least I had those to assist in referencing the position, great fun and learned so much.
take a lesson, luckily my own accidents were sim only and it should always be that way if you practice in the sim and find out what can go wrong before you play in real life. I adjusted my flying and attitude, I was very frightened by the sim impacts enough to be much more cautious irl and recognize where problems might come from.
Not a speech just some anecdotes and advice, keep it real, keep safe, know your limitations and STOP if you feel out of your comfort zone.