Of course internal drills are very, very different from isometric exercises that you would be prescribed by a physical therapist, for instance, but any drill where there is no outside body movement neatly falls into the category of "isometric". The strict definition is met by the standing and partial squat drills done by every internal training group I have seen, for instance.
And any drill in which one breathes is a breathing exercise? ;-)
In my opinion the difference between isometric drills and standing practice (zhan zhuang) is so big, that if you put them in the same category, you're left with quite meaningless category.
OTOH, occasionally I do come across IS explanations that use Western anatomy in the same way as they were using qi, i.e. not as an attempt at scientific explanation, but as a model to shape your practice.
Don't know if this might apply to Tomiki, though.