FWIW, I haven't heard of tai sabaki being used in reference to "internal body skills".
If that's what the kendoka meant, why didn't they say they went to him to learn kokyu, kokyu-ryoku, or ki no nagare or some other more likely term?
While not in aikido circles, I have heard the term tai sabaki used in refering to internal body skills. I've come across a few sensei here in Japan who have made the point that tai sabaki is more or less the gateway to said skills. With that being said, I would also say that the majority of people in Japan I have come in contact with generally just view the word as general "body movement". The impression I get is that it is one of those terms that could be as general or as deep in meaning as you are willing to find in it, much like meaning of "kokyu" can shift in practice and meaning the deeper you get into your given art or how for many people the term "katsujinken" is an abstract budo ideal for peace, while for others it is a concrete and applicable approach used to manipulate the enemy in combat. A lot of budo related terminology can have as much meaning and depth as you are willing to find in it and because one group uses the term one way does not mean that others do not find different nuances in the word.