Are you talking about my video here? I'm recommending grabbing lower on the arm. Maybe I'm miss understanding you.
Yes. You showed both ways of grabbing. Either is easily broken and neither protects you from being seriously wounded (unless the attacker is the someone who trained with you, I suppose...).
Mochizuki Sensei never performed techniques by letting uke hold onto his wrist. Whenever grabbed, his response was always to break uke's grip and re-grasp uke with a twisting grip to turn the arm one way or the other for a technique.
And grabbing the hand that's drawing the sword really could only buy you an instant (less than a second) before the slicing and dicing would commence.