You are correct. I was equating thickness with more plies, which is usually the case but not always. You can have a thin shell with more plies than a thick shell with a few plies.I'm not sure what you are getting at exactly... can you elaborate?
More plies does not always mean thicker shells... You can have a 7mm 6 ply drum shell or a 6mm 7 ply drum shell etc...
And number of plies and shell thickness is only one of many, many factors making up the sound of a drum. More important are bearing edges, drum head selection and tuning.
In terms of thickness, usually, a thinner shell will have slightly woodier tone where a thicker shell will project more and have a bit more volume... but in this case - pay attention to the actual shell thickness - NOT the number of plies.