Grove is modular hardware design for Plug-n-Play with 4-pins socket/interface. So, Grove supports 4 types interface/protocol which just need 4-pins or less IO, UART, Digital IO, Analog IO, I2C.
Unfortunately, SPI consists of 4-pin: MISO, MOSI, CS and CLK. So it can’t be compatible with Grove System.
Actually, SPI as normal Digital IO in Wio Link, you can use SPI as an normal ESP8266 development, but you will lost a lot of features we provide, such as OTA, RESTful API. And also, you have to jumping wire to connecting SPI device.
BTW, here is the IO, not Pin Number(please open the image in new tab) which SPI has on Wio Link: