I have trouble showing and saying what I mean in person when working one to one with my kohai, let alone in type.
I use these two exercises a lot because I consider that they help develop the right posture and body feeling for aikido.
Describing the right posture for aikido should be doable, shouldn't it? Perhaps attach a picture? When you do these exercises, how do you check your posture?
When you start to feel these things, the sensei saying things like "relax", "use your center", "keep extension" stops being gibberish and starts to make sense as you can tie it to actual body feelings you are familiar with.
How do you guarantee/verify that the sensei and you are talking about the same things? If I'm allowed a cynical interpretation: the sensei restricts himself to saying vague stuff, knowing that every student will at one time feel something of which the student will decide that it's what the sensei was trying to explain. And the students that don't experience such moments, will just think they're not good/sensitive/intelligent/etc. enough to get it.