No, of course we don’t microwave the mug WITH the teabag in it. We microwave the teabag separately.
12 points
It may appear that way if it was unevenly heated, causing pockets of boiling water surrounded by comparatively cool water. This would make it look like it’s boiling, but then, when mixed, it is then much cooler than if heated by a kettle that relies on convection to mix the water.