That number still seems a bit too high. According to Statista, the working population in the UK is 32.350.000. This would roughly mean that every tenth person is connected to the App Store. If you include the market share of iOS (50%), it would mean that every fifth person with an iOS device is working in the iOS App economy...
This argument reminds my of the German car lobbyism. They always say that every 7th or 8th job in Germany is connected to the car industry, when in reality, of a working population of ~45.000.000 people, only around 830.000 people are directly working in the car industry - that's like every 55th employment. The calculation they use includes every connection to a car manufacturer they can find, I would argue that Apple does the same.