Spouse with dementia has forgotten how to draw - is this typical?

My 81-year-old husband suffers from vascular dementia, with increasingly poor long- and short-term memory, some hallucinations, and often producing a garbled stream of meaningless words when he talks. He used to be an accomplished artist who drew very well. Recently I got him a drawing book, and now when I suggest he draw something, for example, our dog, instead of a drawing, he will write the words "Our Dog" on the piece of paper. When I say, can you draw the dog? he points to the words and says "I did draw the dog." Is this a typical feature of dementia -- he seems to have forgotten how to draw. Thanks for any insights!