For ascii to look right, not messed up, the generator has to know the width of the div in ascii characters, e.g. 80, 240, etc, so it can make sure the lines don't wrap. So how does an LLM know anything about the UI it's serving? Is it just luck? what if you ask it to draw something that like 16:9 in aspect ratio... would it know to scale it dowm so lines won't wrap? how about loss of details if it does? Also, is it as good with Unicode art? So many questions.
They don't see runs of spaces very well, so most of them are terrible at ASCII art. (They'll often regurgitate something from their training data rather than try themselves.)
And unless their terminal details are included in the context, they'll just have to guess.