For someone so supposedly creative, he does seem to lack an imagination in not being able to think of a more interesting subject to draw.
I see it as a tribute to his grandfather, and that it is a labor of love rather than something to be ridiculed.
It’s an amazing story of the man who compiled those things, one or two at a time over the course of his life.
And it IS interesting to think that the grandson was so touched by his grandfather’s death that he wanted to preserve the things in the shed before they were given away or destroyed.