Product description

I purchased the beautiful International Certified Bloom set of four mugs. The website description states that the product is dishwasher safe and microwave safe. It is also printed on the bottom of each mug along with,"caution: use in microwave might cause product to become hot for reheat only". Why is there a printed warning like this on each mug if it is supposed to be microwave safe? I contacted the manufacturer and their response stated "the product is safe for microwave use, but for reheat only". I am not sure if these mugs can be used in the microwave to boil water for tea or coffee.