This appears to be header images taken from popular or random recent articles within that category, rather than an image specifically chosen to represent the en

This appears to be header images taken from popular or random recent articles within that category, rather than an image specifically chosen to represent the entire category. e.g. For Climate Change they're showing the header for https://medium.com/invironment/an-army-of-ocean-farmers-on-the-frontlines-of-the-blue-green-economic-revolution-d5ae171285a3 https://medium.com/invironment/an-army-of-ocean-farmers-on-t...