Nothing to be sorry about. I skimmed the video (it's a bad habit I have) but I have since gone back and viewed the relevant bits to make sure I didn't miss anything.
I agree the force was being applied in the weakest direction of the tool, I don't agree on the name of the tool (because we call them 'multigrips' in this country).
I think 1/2 inch is understating it a bit, but his fingers were close.
If the tool slips off but stays secure in the multigrips which he is holding, there's no way for the blade to get to his fingers, and if it slips off it is no longer driven so won't have enough momentum to cause much of an injury. If the blade pivots in the multigrips, as we both suspect is possible, the blade could still be driven and may come in to contact with his finger. However, it will also come into contact with the side of the multigrips and this will a) stop it going deeper into his finger and b) stop the blade quickly as he lets go of the whole thing. There'd possibly be an injury but it's likely to be slight. Honestly, I end up with a 'gash' that needs patching at least every couple of weeks, either from bumping a milling cutter, sliding my finger along something I shouldn't or just bashing into something hard. If I don't have to stop working for more than a few minutes then I don't consider it a bad enough injury to worry about.
Isn't this incredibly common, even routine? Mine get far closer when I'm sanding or sometimes filing a workpiece.
I believe there was some risk of injury during this process, but I don't believe it was as heinous as some are suggesting. I also would not recommend a beginner attempt anything like this - just as I wouldn't recommend a beginner do any filing under power, graving, metal spinning or even aluminium casting.
I also don't recommend anyone follow some of the things we commonly see and hear about on the forum from (sometimes) very experienced builders/machinists. For example, we see plenty of photos and videos with visible jewelry, people using and advocating emery cloth for sanding a rotating part and even people defending their use of compressed air to clear chips because "I've been doing it for years".