Azure Functions Flex Consumption has indeed a limit of one function app per plan. The Azure Function Limits documentation has been updated to reflect that. Because the concurrency based scaling of Flex Consumption aims to be deterministic, the product group decided not to allow for multiple function apps in the same plan all voting independently to scale. You can still have different triggered functions inside the same Flex Consumption function app though, and these would scale into their own instances as described in per-function scaling.