Look into the plug holes to see if the contacts to the plug blades are full size brass (good) or half size steel(?) (bad). The latter is a characteristic of the Leviton 279-S00, and tends to risk overheating due to higher resistance. If this is the case, you may have to limit the charging amperage to 24A or lower, depending on the ambient temperature (the mobile connector plug head may detect excess heat and reduce amperage to 16A, although sometimes not before the outlet melts).
Regarding the GFCI breaker, that became required in electrical codes only in the past few years (2017 NEC, adopted at varying times in the next few years after by various states), so an older installation without it may have been code compliant then.
