These leaves of Crassula perfoliata may belong to var. coccinea or to var. minor. Only some of the variations of C. perfoliata display the feature of leaf bases surrounding the stem "by appearing to pass through the substance of the long-lived evergreen leaves", the feature recognised in the specific epithet of perfoliata (per meaning through and folia being leaves).
C. perfoliata var. coccinea has leaves that are different, channelled at the base. This makes these leaves more likely to belong to C. perfoliata var. minor, although they are not grey-green and the plant on which they grow gets rather large.
Borderline cases either get lumped with others in the most likely category, or cause new categories to be created. The more categories, the more grey areas to ponder when considering individual differences! Thus the complexity of nature may be surpassed by the complexity of human classification systems (www.plantzafrica.com).