It’s been known for ages that many people work far less than what is considered to be a “full” week. Some do this because there is nothing else for them. Many do it because it suits them. It also then allows them to claim Working Tax Credits if they work just sixteen hours per week (provided they have children). So, work just under half a week and the taxpayer pays you for the other half.
I wasn’t aware that working just one hour classes you as “employed” but it doesn’t surprise me. As well as that many professional people (doctors, lawyers, dentists, for example) are so well paid that they only need work half a week or less. My dentist works only two days a week and the last GP I saw only works one day a week. So it is no surprise that record numbers of people are “in employment”.
It is interesting to read of the person who was repeatedly sent home after reporting for work because there was nothing for him that day. This is really the modern day equivalent of the “docker’s call on” which was in place to a greater or lesser degree up until 1967. Dockers had to gather at the dock gates to be “called on” by the foremen for a day’s work. Many were left “on the cobbles” (i.e. without work) and ha to return home. The call on was undertaken two or even three times a day. It was the establishment of the National Dock Labour Board in 1947 that saw a decline in the practice but it continued to a lesser degree into the 1960s:
https://islandhistory.wordpress.com/2014/01/08/the-call-on/