A life on stone isn’t necessarily a stony life. Whichever, Hereroa glenensis isn’t bothered.
Succulent leaves in the typical vygie mould make up for the low water retention mostly characterising rock crevices. Small plant size is a blessing living here, free from big plant competition as far as sunlight is concerned. Compact growth forms equip plants for coping with harsh temperature fluctuations. Bright flowers are a benefit when the vegetation is sparse in pollinator alerting terms (Smith, et al, 1998; iNaturalist; https://www.botanikks.com).