Its not your general take on Aikido videos because: "I would find his position on tsubas much more convincing if the linked videos involved attacks that might at least sting a little bit" so there must be something specific in those videos that make it hard for you "to tell much". What is it?
As I said, with beginners, almost anything works. I'm not sure the attacker could hit a wine glass hard or accurately enough to break it, much less connect with or do damage to a moving human target. And so it doesn't really matter whether Graham uses a tsuba or not: his wrist isn't going to get hit hard enough for him to care.