Yep, those CPUs only support 8GB max.
See the Intel Core i7 2620M (the 2.7Ghz part in the high-end 13" model) spec sheet for example: http://ark.intel.com/Product.aspx?id=52231
See the Intel Core i7 2620M (the 2.7Ghz part in the high-end 13" model) spec sheet for example: http://ark.intel.com/Product.aspx?id=52231