In the States indeed these mostly look like bog standard coffee mugs. The tall one exists as a design but it’s rarer. I can’t speak for the OP but my experience

In the States indeed these mostly look like bog standard coffee mugs. The tall one exists as a design but it’s rarer. I can’t speak for the OP but my experience is that media about Great Britain in America often depicts tea mugs as different (I’ve seen many shorter, smaller and flatter variants) than those mugs. Perhaps it is to highlight that the beverage is tea and not something else like coffee to the viewer.