Yes, all plates do get slightly hot to the touch if you're heating for longer than a few minutes.
We recommend using oven gloves or similar to take hot food/plates out of the microwaves. Please use the same caution as you would removing hot dishes from an oven.
How hot your plate will become varies with the wattage of the microwave and the length of time it is heated, as well as whether the food or liquids are direct from the fridge or at room temperature.
It also comes down to the moisture content in the material. Stoneware does have a high retention of air and water in the items even when dried really well and this enhances the direct heat of the plates.