@donkey which is good and one would presume/hope they've thought of visual impairment. Also, a written sign is unlikely to include instructions for those with visual impairment. Of course, this is the age when such inclusion doesn't always happen.
@crimperman indeed - and what is also there is the regular big chunky push button too - this ‘wave your hand’ thing seems specifically for people who don’t want to touch a big yucky button.