PlatformIO only officially supports the official Arduino-ESP32 core made by Espressif, not the spin-off forks from HelTec. Sometimes changes or new boards get merged back into the official core like here, giving them support there, but that doesn’t happen with every board.
For the WiFi_Kit_32 V3, there is however this PR open, and you can import in PlatformIO as already discussed in Heltec Esp32 LoRa v3 board support - #2 by maxgerhardt.
Official merge back in PlatformIO is already tracked in