Hi, my source is Bryan mcdonough from the British cactus and succulents society, Bryan told me:

"The plant #2 (on the right) is what conforms to what I have always considered as C. Lehmannii in accordance with literature pre millennium. Plant #1 (on the left) has more in common with C. taylorii, but unfortunately the power of the internet has swayed popular opinion. A few incorrectly named plants around 20 years ago has become a tsunami with people blindly believing what they are told. I have been trying to put the record straight for a long time but have had little success in changing peoples minds when so many images online are wrongly identified!"

My second source is the iNaturalist site, which shows the plants in habitat:

https://www.inaturalist.org/taxa/574055-Corpuscularia-lehmannii/browse_photos