Top dressing helps keep moisture in the soil by reducing heat and wind related evaporation down. I mostly use the 3/8 & up pieces of pine bark after sifting for gritty mix. I have also used grani-grit and haydite as a decorative element as well. I don't always top dress though. If I don't have anything cheap or preferably repurposed lying around, I ofter don't bother.

Granite will help with the chipmunk issue, the sharp edges are rough oo them, but may not always stop it. It's also good for keeping fungus gnats down, although with the 5-1-1 and gritty mix, I don't see them unless they come in on nursery stock, but they soon disappear without further action on my part.

I have gardened extensively in containers for more than 25 years and I have never topdressed or mulched anything. Unless it is a very small plant or one with an extended trunk in a large sized container, I am not convinced topdressing or mulching has any effect on soil moisture evaporation. In most cases, the container planting fully covers any exposed soil and that is more than enough to offset any assumed moisture evaporation. Even with the trees I grow in containers, which do leaved an exposed area of soil surface, I have not found any need for mulching. It is too confined a surface area to have any significant effect.

I would also be disiclined towards this practice for the same reasons one wants a uniform soil texture in container plantings......layering different soil textures just slows water penetration and good dranage.

btw, every spring I have to dig out horsechestnut seedlings from many of my containers that the squirrels have used to stash their treasures :-) But it is just part of my normal spring care for all my containerd plants.