Hi ashwinivin,
There are some comments about thickness and having more layers in post #14 here that should be helpful.
You certainly aren’t anywhere close to a weight range that would “need” more than 9" of latex to sleep well at night but depending on the specific design of the mattress and the layers inside it and where they are in the range between “princess and the pea” and “I can sleep on anything” there may be some people that would notice a difference and may “prefer” a thicker mattress.
Phoenix